Populations, Their changes and Their measurement

IB syllabus: 2.1.6, 2.3.1, 2.3.2, 2.6.1-2.6.4, 2.7.2

AP syllabus

Ch 9

Syllabus Statements

2.1.6: Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples

2.3.1: Construct simple keys and use published keys for the identification of organisms

2.3.2: Describe and evaluate methods for estimating abundance of organisms

2.6.1: Explain the concepts of limiting factors and carrying capacity in the context of population growth

2.6.2: Describe and explain s and J population curves

2.6.3: Describe the role of density-dependent and density-independent factors and internal and external factors, in the regulation of population

2.6.4: Describe the principles associated with survivorship curves including K and r-strategists

2.7.2: Describe and evaluate methods for measuring change in abiotic and biotic components of an ecosystem due to a specific human activity

Population

A group of individuals of the same species found in the same area at the same time like

The gopher tortoises in scrub habitats in Volusia county

The bottlenose dolphins of the Indian River Lagoon

Sea Otters: A case study

Sea otters keystone species in Pacific kelp forests

Daily consume 25% body weight in urchins & molluscs

1 Population > 1 million before settlers arrived

1700’s hunted to near extinction – 1000 in the Aleutians, AK only 20 off California

In 1971 A-bomb test in AK used sea otter population to assess bomb’s power  1000’s died

1973 Endangered Species Act passes, 1976 Marine Mammal Conservation Act

1989 1000’s died in Exxon Valdez Oil spill

Otters recovering in most places after 1970’s

The spring 2008 survey found 2760 sea otters, down 8.8-percent from the record 2007 spring survey.

Why are they declining now?

Population characteristics

Populations are dynamic – change in response to environment

Size (# of individuals)

Density (# of individuals in a certain space)

Dispersion (spatial pattern of individuals)

Random, Uniform, Clumped  based on food

Age distribution (proportion of each age)

Changes called Population dynamics

Respond to environmental stress & change

Limiting Factors & Population Growth

4 variables govern changes in population size

Birth, Death, Immigration, emigration

2 Variables are dependent on resource availability & environmental conditions

Population change = (Birth + Immigration)– (Death + Emigration)

Capacity for Growth

Capacity for growth = Biotic potential

Rate at which a population grows with unlimited resources is intrinsic rate of increase (r)

High (r)  (1)reproduce early in life, (2)short generation time, (3)multiple reproductive events, (4)many offspring each time

BUT – no population can grow indefinitely

Always limits on population growth in nature

Carrying Capacity

Environmental resistance = all factors which limit the growth of populations

Population size depends on interaction between biotic potential and environmental resistance

Carrying capacity (K) = # of individuals of a given population which can be sustained infinitely in a given area

Limiting Factors

Carrying capacity established by limited resources in the environment

Only one resource needs to be limiting even if there is an over abundance of everything else

Ex. Space, food, water, soil nutrients, sunlight, predators, competition, disease

A desert plant is limited by…

Birds nesting on an island are limited by…

Minimum Values

3 (r) depends on having a certain minimum population size MVP – minimum viable pop.

Below MVP

1 – some individuals may not find mates

2 – genetically related individuals reproduce producing weak or deformed offspring

3 – genetic diversity may drop too low to enable adaptation to environmental changes –bottleneck effect

Forms of Growth

Exponential growth  starts slow and proceeds with increasing speed

J curve results

Occurs with few or no resource limitations

Logistic growth  (1) exponential growth, (2) slower growth (3) then plateau at carrying capacity

S curve results

Population will fluctuate around carrying capacity

Population Growth Curves Ideal

Sketch the two curves and label the parts of the S curve

Carrying capacity alterations 4 In rapid growth population may overshoot carrying capacity

Consumes resource base

Reproduction must slow, Death must increase

Leads to crash or dieback

Carrying capacity is not fixed, affected by:

Seasonal changes, natural & human catastrophes, immigration & emigration

Density Effects

Density Independent Factors: effects regardless of population density

Mostly regulates r-strategists

Floods, fires, weather, habitat destruction, pollution

Weather is most important factor

Density dependent Factors: effects based on amount of individuals in an area

Operate as negative feedback mechanisms leading to stability or regulation of population

External Factors

Competition, predation, parasitism

Disease – most epidemics spread in cramped conditions

Internal Factors

Reproductive effects  Density dependent fertility, Breeding territory size

Natural Cycles: Predation

Over longer time spans populations cycle

Canadian lynx & Snowshoe hare - 10 year cycles

5 Once thought that predators controlled prey #’s  Top down control

Now see a negative feedback mechanism in place  community equilibrium

Reproduction Strategies effect Survival

Asexual reproduction

Produce clones of parents

Common in constant environments

Sexual reproduction

Mating has costs – time, injury, parental investment, genetic errors

Improves genetic diversity  survive environmental change

Different male & female roles in parental care

MacArthur – Wilson Models

Two idealized categories for reproductive patterns but really it’s a continuum r-selected & K-selected species depending on position on sigmoid population curve r-selected species: (opportunists) reproduce early, many young few survive

Common after disturbance, but poor competitors

K-selected species: (competitors) reproduce late, few young most survive

Common in stable areas, strong competitors

r versus K

Most organisms somewhere in the middle

6 Agriculture  crops = r-selected, livestock = K-selected

Reproductive patterns give temporary advantage

Resource availability determines ultimate population size

Survivorship curves

Different life expectancies for different species

Survivorship curve: shows age structure of population

Late loss curve: K-selected species with few young cared for until reproductive age

Early loss curve: r-selected species many die early but high survivorship after certain age

Constant loss curve: intermediate steady mortality

Sketch them

Humans Impact Natural Populations

Fragmenting & degrading habitats

Simplifying natural ecosystems

Using or destroying world primary productivity which supports all consumers

Strengthening pest and disease populations

Eliminating predators

Introducing exotic species

Overharvesting renewable resources

Interfering with natural chemical cycling and energy flow

Sampling populations

7 Step 1: Identify the organism

Use dichotomous keys, field guides, observe a museum collection, or consult an expert http://www.earthlife.net/insects/orders-key.html#key

Sample key for insect ID http://people.virginia.edu/~sos-iwla/Stream-Study/Key/Key1.HTML

Macroinvertebrate key

Construct you Own Dichotomous Key

Mark & Recapture Method

Used for fish & wildlife populations

Traps placed within boundaries of study area

Captured animals are marked with tags, collars, bands or spots of dye & then immediately released

After a few days or weeks, enough time for the marked animals to mix randomly with the others in the population, traps are set again

The proportion of marked (recaptured) animals in the second trapping is assumed equal to the proportion of marked animals in the whole population

Repeat the recapture as many times as possible to ensure accuracy of results

8 Marking method should not affect the survival or fitness of the organism

Mark & Recapture Calculation

# of recaptures in second catch = # marked in the first catch

Total # in second catch Total population (N)

Assuming no births, deaths, immigration, or emigration  population size is estimated as follows (Lincoln Index)

N =

MEMORIZE THIS EQUATION

Example

50 snowshoe hares are captured in box traps, marked with ear tags and released. Two weeks later, 100 hares are captured and checked for ear tags. If 10 hares in the second catch are already marked (10%), provide an estimate of N

**Realize for accuracy that you would recapture multiple times and take an average**

Quadrat Method

Used for plants or sessile organisms

Mark out a gridline along two edges of an area

9 Use a calculator or tables to generate two random numbers to use as coordinates and place a quadrat on the ground with its corner at these coordinates

Count how many individuals of your study population are inside the quadrat

Repeat steps 2 & 3 as many times as possible

Measure the total size of the area occupied by the population in square meters

Calculate the mean number of plants per quadrat. Then calculate the population size with the following equation

Quadrat Method

N =

This estimates the population size in an area

Ex. If you count an average of 10 live oak trees per square hectare in a given area, and there are 100 square hectares in your area, then

In addition to population size we can measure…

Density = # of individuals per unit area

Good measure of overall numbers

Frequency = the proportion of quadrats sampled that contain your species

10 Assessment of patchiness of distribution

% Cover = space within the quadrat occupied by each species

Distinguishes the larger and smaller species

How can changes in these populations be measured?

Necessary because populations may change over time through processes like succession

But also because human activities may impact a population and we want to know how

Impacts include  toxins from mining, landfills, eutrophication, effluent, oil spills, overexploitation

Can still use CMR or quadrat method

Just do it repeatedly over time

Also could use satellite images taken over time

1. Do pre and post impact assessments in one area

2. Measure comparable areas – one impacted, one not at a given time

Capture – Mark - Recapture

Practice Problems

Question 1

In a mark – recapture study of lake trout populations, 40 fish were captured, marked and released. In a second capture 45 fish were caught; 9 of these were marked. What is the estimated number of individuals in the lake trout population

Question 2

Woodlice are terrestrial crustaceans that live under logs and stones in damp soils. To assess the population of woodlice in an area, students collected as many of the animals as they could find, and marked each with a drop of fluorescent paint. A total of 303 were marked. 24 hours later, woodlice

11 were collected again in the same place. This time 297 were found, of which 99 were seen to be already marked from the first time. What approximately, is the estimated population of woodlice in this area?

Review points

Dispersion patterns

Carrying capacity and limiting factors r and K selection

Natural population cycles

Human effects

http://www.otterproject.org

Succession

IB Syllabus: 2.3.5 – 2.3.7

Ch. 8

Syllabus Statements

2.1.6: Define the terms species, population, habitat, niche, community, ecosystem with reference to a named example

2.6.5 – Describe the concept and process of succession in a named habitat

2.6.6 – Explain the changes in energy flow, gross and net productivity, diversity and mineral cycling in different stages of succession

2.6.7 – Describe the factors affecting the nature of climax communities

Community

A group of populations interacting in a particular area

12 The fish community of Ponce Inlet

The plant community of the scrub habitat

Communities Change

Ecological Succession: the gradual change in species composition of a given area over time

Species do change spatially within an area at a certain point in time, this is zonation not succession

2 Types depending on start point

Primary succession: gradual establishment of biological communities on lifeless ground

Secondary succession: reestablishment of biotic communities in an area where they already existed

Zonation II

Horizontal bands or zones of animals and organisms

Vertical layers in a rainforest

Differing plant communities as you go up a mountain

Created by physical and biological factors

Change in these factors is called an environmental gradient

In a rocky intertidal zone these would be

Drying (tides), salinity, competition, grazing

So how could you measure changes in biota along an environmental gradient?

Biota = living organisms

Change in benthic (bottom) community of rocky intertidal with increased depth

Gradient in moisture or drying

Use modified quadrat method run transect into deeper water

13 At set depths place quadrat and sample organisms

Do repeated transects along your sample area

Calculate differences in communities with depth

Primary Succession

Begins in area with no soil on land, no sediment in water

Cooled lava, bare rock from erosion, new ponds, roads

Must be soil present before producers consumers and decomposers can exist

Pioneer Communities

Lichens and Mosses

Survive on nutrients in dust and rock

Start soil formation

Trap small particles

Produce organic material - photosynthesis

Chemically weather the rock

Patches of soil form

Seral Stages: Early Successional Plant Species

Small perennial grasses and herbs colonize, wind blown seeds

Grow close to the ground

Est. large pop. quickly in harsh conditions

Short lived

Break down rock

Seral Stages: Mid to Late Successional Species

14 After 100’s of years soil deep enough

Moisture & nutrients

Also called Seral Community

Shrubs then trees colonize

Trees create shade

Shade tolerant species establish

Seral stages

A seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community.

An example of seral communities in secondary succession is a recently logged coniferous forest; during the first two years, grasses, heaths and herbaceous plants such as fireweed will be abundant, after a few more years shrubs will start to appear about six to eight years after clearing, the area is likely to be crowded with young birches.

Each of these stages can be referred to as a seral community.

Climax community

Characterized by K-selected species

Determined by climate in the area – temperature, weather patterns

Edaphic factors – saturated wet, mesic, arid

Climax community structure is in stable equilibrium for each area

Humans & other factors may maintain an equilibrium below climax

E.g. current warming trends make climax rainforest communities w/ softer wood, faster growing species

End Result = Complex Community

Complex community mix of well established trees shrubs and a few grasses

15 Disturbance may change the structure

Fire, Flood, Severe erosion, Tree cutting, Climate change, Grazing, habitat destruction

Natural or Human processes

Specific successional stage is dependent on the frequency of disturbance

Disturbance and Diversity

Disturbance = any change in conditions which disrupts ecosystem or community structure

Catastrophic or Gradual

Disturbance eliminates strong competitors allowing others a chance

Promotes diversity

Intermediate disturbance  greatest diversity

The intermediate disturbance hypothesis (graph it)

Secondary Succession

Begins when natural community is disturbed BUT soil & sediment remains

Abandoned farms, burned forests, polluted streams

New vegetation can germinate from the seed bank

In both cases succession focuses on vegetation changes

What changes occur through Succession?

16 1. Diversity

Starts very low in harsh conditions few species tolerate – r selected species types

Middle succession mix of various species types – most diverse (role of disturbance)

Climax – k selected species strong competitors dominate

2. Mineral Cycling

Pioneer, physical breakdown & make organic, Later processing increase – cycles expand

3. Gross productivity changes (total photosynthesis)

Pioneer = Low density of producers at first

Middle & climax = high  lots of producers and consumers

4. Net Productivity (G – R = N)

Pioneer = little respiration so Net is large  system is growing, biomass accumulating

Middle & climax = respiration increases dramatically  N approaches zero (P:R = 1)

5. Energy flow

# of trophic levels increases over time

Energy lost as heat increases with more transfers

Graph these changes in successional time

17 Factors in Succession

Facilitation

One species makes an area suitable for another in a different niche

Legumes add nitrogen so other plants thrive

Inhibition

Early species hinder establishment and growth of later species  more disturbance needed to continue

Allelopathy by plants is an example

Tolerance

Late successors not affected by earlier ones

Explains mixture of species in Climax Communities

Predictability of Succession

Generally predictable end of succession is a Climax community

Only real rules are Continuous change, Instability, and unpredictability

Ever changing mosaic of patches in different successional stages

No real progression to an end, rather we see a reflection of an ongoing battle for resources and reproductive advantage

Ecological Stability & Sustainability

Maintained by constant dynamic change

Positive and Negative feedback systems

Community may change but you will still recognize it as a particular type of community

Inertia = The ability of a living system to resist disturbance

Constancy = the ability of a system or population to keep its numbers within limits imposed by resources

Resilience = the ability of a system to bounce back after a disturbance 18 Diversity vs. Stability

Once thought that higher diversity = more stability for a community or ecosystem

Recent studies by D. Tilman on grasslands suggest

More species  higher NPP  more stable

Population #’s for individual species in diverse ecosystems fluctuate more widely

Some level of diversity does provide insurance against disasters

Nature is in a continual state of change

The Precautionary Principle

Human disturbances are disrupting ecosystem processes

Our ignorance of long term effects means we should be cautious

Thus, “When there is considerable evidence that and activity threatens human and ecosystem health, we should take precautions to minimize harm, even if the effects are not fully known.”

Better safe than sorry…

The following succession info is bonus material – if it helps use it if not then don’t

Hydrosere

A hydrosere is simply a succession which starts in water. A wetland, which is a transitional area between open freshwater and dry land, provides a good example of this and is an excellent place to see several stages of a hydrosere at the same time.

In time, an area of open freshwater such as a lake, will naturally dry out, ultimately becoming woodland. During this process, a range of different habitats such as swamp and marsh will succeed each other.

This succession from open water to climax woodland is likely to take at least two hundred years (probably much longer). Some intermediate stages will last a shorter time than others. For instance, swamp may change to marsh within a decade or less. How long it takes will depend largely on the amount of siltation occurring.

19 http://www.countrysideinfo.co.uk/successn/hydro.htm

Hydrosere

Halosere

The term Halosere is an ecological term which describes succession in a saline environment. An example of a halosere would be a salt marsh.

In river estuaries, large amounts of silt are deposited by the ebbing tides and inflowing rivers.

The earliest plant colonizers are algae and eel grass which can tolerate submergence by the tide for most of the 12-hour cycle and which trap mud, causing it to accumulate. Two other colonisers are salicornia and spartina which are halophytes -i.e. plants that can tolerate saline conditions. They grow on the inter-tidal mudflats with a maximum of 4 hours' and exposure to air every 12 hours.

Spartina has long roots enabling it to trap more mud than the initial conlonizing plants and salicornia, and so on. In most places this becomes dominant vegetation. The initial tidal flats receive new sediments daily, are waterlogged to the exclusion of oxygen, and have a high pH value.

The sward zone, in contrast, is inhabited by plants that can only tolerate a maximum of 4 hours submergence everyday (24 hours). The dominant species here are sea lavender and other numerous types of grasses.

Halosere

Xerosere

Xerosere is a plant succession which occurs in conditions limited by water availability or the different stages in a xerarch succession.

Xerarch succession of ecological communities originated in extremely dry situation such as sand deserts, sand dunes, salt deserts, rock deserts etc.

A xerosere may include lithoseres and psammoseres.

Psammoseres

In geography, a psammosere is a sand sere - an environment of sand substratum on which ecological succession occurs.

20 In a typical succession on a sea-coast psammosere, the organisms closest to the sea will be salt tolerant species such as littoral algae and glasswort. Progressing inland the succession is likely to include meadow grass, sea purslane, and sea lavender eventually grading into a typical non-maritime terrestrial eco-system. www.sanddunes.20m.com/Evolution%20.htm

Community Ecology

IB: 2.1.6, 2.1.7

Ch. 8

Videos – extinction clip on exotics, clip on coral reefs

Syllabus Statements

2.1.6: Define the terms species, population, community, niche and habitat with reference to local examples

2.1.7: Describe and explain population interactions using examples of named species

Definitions

Population  a group of individuals of a certain species in a given area at a given time: blue crabs in the Halifax river

Community  interacting groups of populations in an area: the scrub community on campus

21 Species  a group of individuals who can interbreed to produce fertile, viable offspring: FL panthers

Niche  The role of an organism in its environment (multidimensional): nocturnal predator of small mammals in the forest

Habitat  Where an organism typically lives: mangrove swamps

Community Structure

Consider the spatial distribution of organisms

Physical appearance: Size, stratification, distribution of populations and species

Species diversity and richness: number of different species

Species abundance: number of individuals of each species

Niche structure: number, uniqueness and interaction of niches available

Community Differences

Aquatic systems  deep ocean, sandy beach, lakes, rivers, wetlands

Physical structure varies

Most habitats are mosaics, vegetation patches

Sharp edges or broad ecotones (transition zones)

Physical properties differ at edges = edge effect

Forest edge may be sunnier, drier, warmer different species at the edge

Many wild game species found here

Edges can fragment habitat  vulnerability & barriers

What is a niche

The organisms role in its environment

How it responds to the distribution of resources 22 Many dimensions to it – therefore an n-dimensional hypervolume

No two species can occupy the same niche for any period of time

If a niche is vacant organisms will quickly adapt to fill it

Fundamental Niche  Everything that the organism could possibly do given a competitor free environment

Realized Niche  Everything the organism does after competition limits them

Biodiverse Communities

Top species rich environments are tropical rainforests, coral reefs, deep sea, large tropical lakes

Usually high diversity but low abundance

Factors for increased diversity

Latitude: most diverse near equator

Depth: marine communities peak about 2000m

Pollution: more pollution  less species

On land increases in solar radiation, precipitation, seasonal variation, decreased elevation

The Island Effect

Isolated ecosystems studied by MacArthur and Wilson in 1960’s

Diversity effected by island size & degree of isolation

Island Biogeography theory: diversity effected by

Rate of species immigration to island

Rate of extinction on island

Equilibrium point = species diversity

Island Biogeography 23 Immigration and Extinction Effected by

Size: small island has less immigration (small target),

Small island has fewer resources, more extinction

Distance from mainland:

Closer to mainland  more chance of immigration

Applied in conservation for “habitat islands” like national parks surrounded by development

Island Biogeography Data

South Pacific Islands study looked at bird diversity as distance from New Guinea increased

Caribbean Island study found bigger islands had more species diversity than smaller islands which were otherwise similar

Communities have different “Types” of Species

Native species = species that normally live and thrive in a particular community

Nonnative species = species that are accidentally introduced into an area

Keystone species = species that are more important than their abundance or biomass suggest

Indicator species = species that serve as early warnings of damage in a community

Nonnative Species

Also called exotics, aliens, or introduced sp.

FL examples include fire ants, hydrilla, potato vine, peacock bass, …

Occupy niches excluding native organisms

Reproduce rapidly in absence of natural predators

Usually are very adaptable to human disturbed environments

Common Florida Exotics

Indicator Species 24 Mostly species that respond quickly to changes in the environment

Birds indicate tropical forest destruction

Trout indicate pollutant presence in water

Amphibians are a classic indicator

Frogs case study p 170

Frog decline and deformities

Keystone Species

Strong interactions with other species affect the health and survival of those species

They process material out of proportion to their numbers

Roles include: pollination, seed dispersion, habitat modification, predation by top carnivores, efficient recycling of animal waste

Sea Otters

Habitat modification

Elephants – knock over trees in savannah to promote grass growth & recycle nutrients

Bats & birds – regenerate deforested areas by depositing plant seeds in their droppings

Beavers – create ponds forming habitats for many pond dwelling species like fish, ducks, & muskrats

Top predators  exert stabilizing effect by feeding on and regulating certain species

Wolves, leopards, lions, gators, sharks, otters

Over 300+ species are found on the wolf kills made in Yellowstone http://www.wolfquest.org/index.php

Waste removal

Species Interactions

Interactions may be harmful, beneficial, or have no effect at all

Competition: Intraspecific or Interspecific 25 Predation, Mutualism (Symbiosis), Commensalism, Parasitism

Intraspecific Competition

Competition between members of the same species for a common resource

Resource: food, space, mates, etc.

Territoriality

Organisms patrol or mark an area

Defend it against others

Good territories have

Abundant food, good nesting sites, low predator pop.

Disadvantage = Energy, Reduce gene pool

Territoriality Examples

Interspecific Competition

2 or more different species involved

Competing for food, space, sunlight, water, space, nesting sites or other limited resource

If resources abundant, they can be shared but in nature they are always limited

If fundamental niches overlap  competition

One of the species must…

Migrate if possible

Shift feeding habits or behavior = Evolve

Suffer a sharp population decline

Become extinct

Connell’s Barnacles

Methods of competition

26 Interference

One species limits access of others to a resource, regardless of its abundance

Hummingbird territoriality, Desert plant allelopathy

Exploitation

Species have equal resource access, differ in speed of use

Quicker species = more of it & hampers growth, reproduction and survival of other species

Allelopathy

Competitive Exclusion Principle

One species eliminates another in an area through competition for limited resources

Two Paramecium species

Identical conditions grown apart both do well

Grown together one eliminates the other

The niches of two species cannot overlap significantly for a long period of time

Avoiding Competition

Resource partitioning = dividing of scarce resources to species at different

Times

Methods of use

Different locations

Species occupy realized niche, a small fraction of their fundamental niches

Lions vs leopards, hawks vs. owls

Predation

27 Members of one species feed directly on all or part of a living organism of a different species

Individuals  predator benefits, prey harmed

Population  prey benefits: take out the weak, greater resource access, improved gene pool

Predator plays important ecological role

Predation

Predation strategies

Herbivores – sessile prey, no need to hurry

Pursuit – speed (cheetah), eyesight (eagles), cooperation (wolves)

Ambush – camouflage for hiding (praying mantis), lures (anglerfish)

Ambush Predators

Prey defenses

Camouflage – change color, blend with environment,

Chemical warfare – produce chemicals which are poisonous, irritating, bad smelling or tasting

Warning coloration – bright colors advertise inedibility (mimics take advantage of this)

Behavioral strategies – Puffing up, mimicking predators, playing dead, schooling

Warning coloration

Batesian mimicry

Mullerian mimicry

Parasitism

One species feeds on part of another organism (the host) without killing it

Specialized form of predation

Parasite Characteristics

Usually smaller than the host

Closely associated with host

28 Draws nourishment from 7 slowly weakens host

Rarely kills the host

Examples = Tapeworms, ticks, fleas, fungi

Parasites

Mutualism

Symbiotic relationship where both species benefit

Pollination, Nutrition, Protection are main benefits

Not really cooperation, both benefit by exploiting the other

Mutualism II

Examples

Lichens – fungi & algae living together  food for one, structure for the other

Plants and Rhizobium bacteria  one gets sugars the other gets nitrogen

Oxpeckers and Rhinos  food for one, less parasites for the other

Protists and termites  break down wood for one, nutrients for the other

Human Intestinal Symbionts

Commensalism

One species benefits the other is neither harmed nor helped

Examples

Herbs growing in the shade of trees

Birds building nests in trees

Epiphytes = “Air plants” which attach themselves to the trunk or branches of trees

-they have a solid base to grow on and better access to sunlight & rain

29 Energy in Ecosystems II

IB syllabus: 2.1.1-2.1.5, 2.2.1, 2.2.3

A.1.1, A.1.2

AP syllabus

Ch. 4

Syllabus Statements

2.1.1: Distinguish between biotic and abiotic (physical) components of an ecosystem

2.1.2: Define trophic level

2.1.3: Identify and explain trophic levels in food chains and food webs selected from a local environment

2.1.4: Explain the principles of pyramids of numbers, pyramids of biomass and pyramids of productivity, and construct pyramids from given data

2.1.5: Discuss how the pyramid structure effects the functioning of an ecosystem

Syllabus Statements

2.2.1: List the significant abiotic (physical) factors of an ecosystem

2.2.3: Describe and evaluate methods for measuring at least three abiotic factors in an ecosystem

2.3.3: Describe and evaluate methods for estimating the biomass of trophic levels in an ecosystem

Syllabus Statements

2.5.1: Explain the role of producers consumers and decomposers in an ecosystem

2.2.3: Describe and explain the transfer and transformation of energy as it flows through an ecosystem

Ecosystems

Are communities and their interactions with the abiotic environment

30 Ecosystem Components

2 parts

Abiotic – nonliving components

(water, air, nutrients, solar energy)

Biotic – living components

(plants, animals, microorganisms)

Biota

Significant abiotic factors

What abiotic factors effect this Aquatic food chain?

The abiotic influence

Species thrive in different physical conditions

Population has a range of tolerance for each factor

Optimum level  best for most individuals

Highly tolerant species live in a variety of habitats with widely different conditions

The Law of Tolerance: The existence, abundance and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by

31 that species

Abiotic factors may be Limiting Factors (2.6.1)

Limiting factor – one factor that regulates population growth more than other factors

Too much or too little of an abiotic factor may limit growth of a population

Determines K, carrying capacity of an area

Examples

Temperature, sunlight, dissolved oxygen (DO), nutrient availability

Techniques to measure abiotic factors

Terrestrial

Light intensity or insolation ( lux) – light meter; consider effect of vegetation, time of day…

Temperature (°C) – themometer; take at different heights, points, times of day, seasons…

Soil moisture (centibars) – tensiometer of wet mass dry mass of soil; consider depth of soil sample, surrounding vegetation, slope…

Aquatic (specify marine or fresh)

Salinity (ppt) – hydrometer; consider role of evaporation

Dissolved Oxygen (mg/L) – DO meter, Winkler titration; consider living organisms, water circulation, pH – pH probe or litmus paper; consider rainfall input, soil and water buffering capacity

Turbidity (FTU) – Secchi disk or turbidity meter; consider water movement,

Techniques (2.2.2)

For any of them you should know the following

What apparatus is used for measurement and its units

How it would vary or be used to measure variation along an environmental gradient

Scientific concerns about its implementation

32 Evaluation of its effectiveness or limitations

Terminology and Roles of Biota

Producers (Autotrophs) – Through photosynthesis convert radiant to chemical energy (energy transformation)

Consumers (Heterotrophs) – Must consume other organisms to meet their energy needs

Herbivores, Carnivores, Omnivores, Scavengers, Detritivores

Decomposers – Break down organisms into simple organic molecules (recycling materials)

Food chains and Food webs

Food chain  Sequence of organisms each of which is the source of food for the next

Feeding levels in the chain  Trophic levels

First trophic level = producer

Second trophic level = consumer, herbivore

Third trophic level = consumer, carnivore

Highest trophic level = top carnivore

Arrows indicate direction of energy flow!!!

Decomposers are not included in food chains and webs

For complexity of real ecosystem need food web which shows that individuals may exist at multiple trophic levels in a system (omnivores)

Figure 53.10 Examples of terrestrial and marine food chains

Local examples write them in

33 Food Web

Summarizes the trophic relationships of a community through a diagram

Food chain  web, once a given species enters the web at multiple trophic levels

Most consumers are not exclusive to one level (ex. we are omnivores)

Figure 53.11 An antarctic marine food web: Identify the trophic levels

Antarctic pelagic (open ocean) community found in seasonally productive Southern Ocean

Zooplankton: dominant herbivores in Antarctic are euphausids (krill) and herbivorous plankton called copepods

The zooplankton are eaten by carnivores including penguins, seals, fish, baleen whales

Carnivorous squid feeding on fish and zooplankton are important link in food web

Seals and toothed whales eat squid

During whaling years humans became top predators in the system

Entire food web depends on phytoplankton  photosynthesizing microorganisms obtaining energy from the sun

Food Webs

Food webs are limited by the energy flowing through them and the matter recycling within them

Ecosystem is an energy machine and a matter processor

34 Autotrophs: make their own food (plants algae & photosynthetic prokaryotes)

Heterotrophs: directly or indirectly depend on photosynthetic output of primary producers

Producers

Transform energy into a usable form

Starting form may be light energy or inorganic chemicals

Turned into organic chemical energy

This is the form that is used at other trophic levels

Photoautotrophs

Consumers

Heterotrophs: get energy from organic matter consumed

Primary, Secondary & Tertiary consumers

Herbivores  primary consumers, eat plant material e.g. – termites, deer

Carnivores  other consumer levels, eat animal material e.g. eagles, wolves

Omnivores  consumers eating both e.g. bears

Figure 53.0 Lion with kill in a grassland community

Decomposition

Decomposers obtain energy by breaking down glucose in the absence of oxygen

Anaerobic respiration or fermentation

End products = methane, ethyl alcohol, acetic acid, hydrogen sulfide

Matter recycling  inorganic nutrients returned to producers

Decomposition Process

Consumers or Decomposers 35 Detritivores = get their energy from detritus, nonliving organic material  remains of dead organisms feces, fallen leaves, wood

May link producers to consumers

Dung beetles, earth worms

Saprophytes = feed on dead organic material by secreting digestive enzymes into it and absorbing the digested products

Producers can reassimilate these raw materials

Fungi (mold, mushrooms), bacteria

Energy in living systems

Food chains, webs and pyramids, ultimately show energy flow

Obey the laws of thermodynamics

Obey systems laws – input, transfer, transformation, output

Thermodynamics Review

Universal laws that govern all energy changes in the universe, from nuclear reactions to the buzzing of a bee.

The 1st law: Energy can be transferred and transformed but not created or destroyed

- Energy flow in the biological world is unidirectional:

Sun energy enters system and replaces energy lost from heat

Energy at one trophic level is always less than the previous level

The 2nd law: Energy transformations proceed spontaneously to convert matter from a more ordered, less stable form, to a less ordered, more stable form

Energy lost as heat from each level

36 Energy at one level less than previous because of these lossed

Energy Flow in Communities

Energy unlike matter does not recycle through a community  it flows

Energy comes from the sun

Converted by autotrophs into sugars

Amount of Light energy converted into chemical energy by autotrophs in a given time period  Gross

Primary Production GPP

The amount to pass on to consumers after plants have used their share  Net Primary Production NPP

NPP = GPP - R

The Source of All energy on Earth is the …

Figure 3-10 Page 52

What is the sun?

72% hydrogen, 28% helium

Temp and pressure high so H nuclei fuse to form He releasing energy

Fusion energy radiated as electromagnetic energy

Earth receives 1 billionth of the suns Energy

Most reflected away or absorbed by atmospheric chemicals

Energy to Earth 37 30% solar energy reflected back into space by atmosphere, clouds, ice

20% absorbed by clouds & atmosphere

50% remaining

Warms troposphere and land

Evaporates and cycles water

Generates wind

< 0.1% captured by producers for photosynthesis

Energy eventually transformed to heat and trapped by atmosphere “Natural Greenhouse Effect”

Eventually reradiated into space

So if sunlight in = sunlight + heat out

What state is the system in?

Stable Equilibrium

Summary of solar radiation pathways – sketch it

38 Incident radiation comes in, it is then…

Lost by reflection (ice caps) and absorption (soil, water bodies)

Converted from light to chemical energy (photosynthesis in producers)

Lost as chemical energy decreases through trophic levels

Through an ecosystem completely converted from light energy into heat

Reradiated as heat back to the atmosphere

Energy Flow II

Energy measured in joules or kilojoules per unit area per unit time

Energy conversion never 100% efficient

Some energy lost as heat

Of visible light reaching producers, only 1% is converted to chemical energy

Other levels are 10% efficient – only assimilate %10 of energy from previous level

Figure 54.1 An overview of ecosystem dynamics

Energy Flow and Food webs

Biomass = the total dry weight of all organisms in one trophic level

Usable energy degraded with each transfer

Loss as heat, waste, metabolism

% transferred = ecological efficiency  ranges from 5-20%

More trophic levels = less energy available at high levels 39 Energy Flow through Producers

Producers convert light energy into chemical energy of organic molecules

Energy lost as cell respiration in producers then as heat elsewhere

When consumers eat producers energy passes on to them

In death organic matter passes to saprophytes & detritivores

Energy Flow through Consumers

Obtain energy by eating producers or other consumers

Energy transfer never above 20% efficient, usually between 10 – 20%

Food ingested has multiple fates

Large portion used in cell respiration for meeting energy requirements (LOSS)

Smaller portion is assimilated used for growth, repair, reproduction

Smallest portion, undigested material excreted as waste (LOSS)

Figure 54.10 Energy partitioning within a link of the food chain

Energy flow through Decomposers

Some food is not digested by consumers so lost as feces to detritivores & saprophytes

Energy eventually released by process of cell respiration or lost as heat

Construct and analyze energy flow diagrams for energy movement through ecosystems

Trophic level boxes are storages – biomass per area (g m-2)

Energy Flow in arrows – rate of energy transfer

(g m-2 day-1)

40 Using Pyramids to express ecosystem dynamics

Pyramids

Graphic models of quantitative differences between trophic levels

By second law of thermodynamics energy decreases along food webs

Pyramids are thus narrower as one ascends

Pyramids of numbers may be different  large individuals at low trophic levels – large forests

Pyramids of biomass may skew if larger organisms are at high trophic levels  biomass present at point in time – open ocean

Losses in the pyramid

Energy is lost between each trophic level, so less remains for the next level

Respiration, Homeostasis, Movement, Heat

Mass is also lost at each level

Waste, shedding, …

Pyramids of Biomass

Represents the standing stock of each trophic level (in grams of biomass per unit area g / m2)

Represent storages along with pyramids of numbers

How do we get the biomass of a trophic level to make these pyramids?

Why can’t we measure the biomass of an entire trophic level?

Take quantitative samples – known area or volume

Measure the whole habitat size

Dry samples to remove water weight

Take Dry mass for sample then extrapolate to entire trophic level

Evaluation  It is an estimate based on assumption that 41 all individuals at that trophic level are the same

The sample accurately represents the whole habitat

Pyramids of Numbers

Needs sampling similar to Biomass and therefore has the same limitations

Also measures the storages

Pyramids of productivity

Flow of energy through trophic levels

Energy decreases along the food chain

Lost as heat

Productivity pyramids ALWAYS decrease as they go higher – 1st and 2nd laws of thermodynamics

Shows rate at which stock is generated at each level

Productivity measured in units of flow (J / m2 yr or g / m2 yr )

Figure 54.11 An idealized pyramid of net production

Figure 54.14 Food energy available to the human population at different trophic levels

Take an Economic Analogy

1. If you look at the turnover of two retail outlets you can’t just look at the goods on the shelves

Rates of stocking shelves and selling goods must be known as well

A business may have substantial assets but cash flow may be limited

42 So our pyramids of Biomass and numbers are like the stock or the assets and our pyramids of Productivity are like our rate of generation or use of the stock

How does pyramid structure effect ecosystem function?

Limited length of food chains

Rarely more than 4 or 5 trophic levels

Not enough energy left after 4-5 transfers to support organisms feeding high up

Possible exception marine/aquatic systems b/c first few levels small and little structure

Vulnerability of top carnivores

Effected by changes at all lower levels

Small numbers to begin with

Effected by pollutants & toxins passed through system

Effects II: Biomagnification

Mostly Heavy metals & Pesticides

Insoluble in water, soluble in fats,

Resistant to biological and chemical degradation, not biodegradable

Accumulate in tissues of organisms

Amplify in food chains and webs

Sublethal effects in reproductive & immune systems

Long term health effects in humans include tumors, organ damage, …

Practice Problems

The insolation energy in an area of rainforest is 15,000,000 cal/ m2/day. This is the total amount of sun energy reaching the ground. The GPP of the producers in the area, large rainforest trees, is 0.0050

43 g/cm2/day and 25% of this productivity is consumed in respiration. By laboratory tests we found that 1 gram of rainforest tree contains 1,675 calories of energy.

A. What trophic level are the trees considered? (2 point)

B. Calculate the NPP of the system. (5 point)

C. Find the efficiency of photosynthesis. (5 point)

D. If a monkey population eats the fruit from the trees how many square meters of forest will each individual need to feed in if they require 400 calories each day?

Practice

Create a food web for the following FL organisms

largemouth bass, panther, racoon, white tailed deer, bullfrog, shiner (small fish), water beetles, zooplankton, phytoplankton, marsh grass, rabbit, water moccasin, dragonfly, duckweed, egret, wood duck,

http://www.indianriverlagoon.org/stats.html

Cycling of matter

IB Syllabus: 2.2.3, 2.2.6

Ch. 4

Syllabus Statements

2.5.4: Describe and explain the transfer and transformation of materials as they cycle within an ecosystem

Biogeochemical cycles

Nutrients needed for life are continuously cycled between living and nonliving things

Life  Earth  Chemical cycles

44 Driven by incoming solar energy

Connect past – present – future by recycling chemical compounds

Oxygen, Carbon, Nitrogen, Phosphorous, and water

Water Cycle

Collects, purifies and distributes earth’s constant water supply

Evaporation – converts water into vapor

Transpiration – evaporation from plant leaves

Condensation – vapor to liquid

Precipitation – rain, sleet, snow, hail

Infiltration – movement of water into soil

Percolation – flow of water to aquifers

Runoff – movement of water over land surface

Sun powers the cycle – 84% vapor from ocean

Warmer air holds more water

Relative humidity = amount of water vapor in a mass of air expressed as a % of the maximum the air could support at that temp

Wind and air masses transport water around the earth

Precipitation – needs condensation nuclei to occur

Soil dust, volcanic ash, smoke, sea salt, particulates

Some locked in glaciers, most into oceans as surface runoff

Runoff sculpts earth’s surface & transports nutrients

Water purification happens at many steps

Human Influences 45 Withdrawing large quantities of fresh water from surface and ground water

Aquifer depletion and saltwater intrusion

Clearing vegetation for agriculture, mining, construction

Increase runoff, flooding, erosion, Decrease infiltration

Modifying water quality

Adding nutrients, changing natural processes

Systems model: Water Cycle

Carbon cycle

“C” is the basic building block of life

Global gaseous cycle based on CO2

Producers remove CO2 from the atmosphere in photosynthesis

Respiration of organisms puts CO2 back into atmosphere

46 Organic carbon stored in living tissues and fossil fuel deposits

Terrestrial Carbon cycle

Carbon storages

Organisms store most of the carbon organic compounds

Sedimentary rocks such as limestone

Carbon reenters cycle when sediments dissolve naturally or by acid rain

Oceans

Gas dissolves into ocean at surface

Removed by marine algae in photosynthesis

Marine organisms

Reaction of CO2 with Ca in organisms to produce CaCO3 for shells and

Human effects

Adding Carbon to the Atmosphere

Clearing trees and plants that absorb CO2 through photosynthesis

Burning fossil fuels and wood increasing CO2

Enhance the greenhouse effect

Raise sea level

Disrupt food production

Destroy habitats

Systems model: Carbon Cycle

47 Nitrogen cycle

1. Nitrogen Fixation

Specialized bacteria convert atmospheric N2 into NH3

N2 + 3 H2  2 NH3

Done by

Cyanobacteria – in soil and water

Rhizobium – bacteria living in root nodules of a variety of legume plants

2. Nitrification

A two step process

Ammonia in soil converted to nitrite and nitrate

48 Aerobic bacteria complete this process

NH3  NO2- (toxic to plants)

NH3  NO3- (easily taken up by plants as nutrient

3. Assimilation

Plant roots absorb inorganic nitrogen ions nitrates, ammonium

Ions used to make nitrogen containing organic molecules

DNA, amino acids, proteins

Animals get nitrogen by eating plants or other plant-eating animals

4. Ammonification

After N has been used in living things and it leaves as waste or death…

Bacterial decay results

Producing

Simpler inorganic compounds like NH3

Water soluble salts containing NH4+

5. Denitrification

Anaerobic bacteria in waterlogged soils and bottom sediments

Convert nitrogen compounds back into gas forms and release into the atmosphere

NH3 NO2- N2

 

NH4+ NO3- N2O

49 Human effects on the N-cycle

Inputs of commercial inorganic fertilizer

Adding NO to the air through combustion of fuels

Enters water cycle  Acid Rain

Removing “N” from the crust by mining

Removing “N” from soil

Harvest crops, irrigation, deforestation

Adding “N” to aquatic systems from runoff

Systems model: Nitrogen Cycle

The Phosphorous cycle

Through water  organisms  earth’s crust

Very little in the atmosphere

50 Found as phosphate salts in terrestrial rocks and ocean sediments

Into organisms by uptake & assimilation by plants, consumption & assimilation by animals, then animal waste returns it to water or to the land (guano)

Often a limiting factor in plant growth both terrestrial and aquatic

Human effects

Mining large amounts of phosphate rock

Inorganic fertilizers, Detergents

Reducing available phosphate in tropical forests by removing trees

Soil nutrients washed away w/out trees

Adding excess phosphate to aquatic systems

Runoff of animal waste, commercial fertilizer from farmland, municipal sewage discharge

Florida Phosphate mining

Systems model: Phosphorous Cycle

The sulfur cycle

Most “S” stored underground in rocks and minerals including salts in ocean sediment

Enters the atmosphere from volcanoes, sea spray, decomposition in aquatic habitats

Marine algae may produce DMS sulfur compounds in large quantities

In atmosphere it may mix into hydrologic cycle to form sulfuric acid – acid rain 51 Human effects

Burning “S” containing coal and oil for electricity production

2/3 of human SO2 inputs

Refining “S” containing petroleum into gasoline, heating oil, etc.

Smelting of “S” compounds of metallic minerals producing pure metals

Copper, Lead, Zinc

Cycle types

With all cycles common features allow grouping

Groups based on storages

Sedimentary cycle – major storage in the ground

E.x. phosphorous cycle

Atmospheric cycle – major storage in the atmosphere

E.x. nitrogen cycle

You should be able to create a flow diagram of Carbon, Water and Nitrogen cycles

http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html

Ecosystem Productivity

IB Syllabus: 2.2.1-2.2.6, A.3.1, A.3.2, A.2.3

AP

Chapter 4

52 Syllabus Statements

2.5.2: Describe photosynthesis and respiration in terms of inputs, outputs and energy transformations.

2.5.5: Define the terms gross productivity, net productivity, primary productivity, and secondary productivity

2.5.6: Define the terms and calculate the values of gross primary productivity (GPP) and net primary productivity (NPP) from given data.

2.5.7: Define the terms and calculate the values of gross secondary productivity (GSP) and net secondary productivity (NSP) from given data.

Figure 10.1 Photoautotrophs

Photosynthesis in Plants

Chloroplasts are the location of photosynthesis in plants

In all green parts of plants – leaves, stems,…

Green color from chlorophyll (photosynthetic pigment)

Found in cells of mesophyll – interior tissue of leaves

Gases exchanges through the stomata

Water enters through xylem of roots

Figure 10.2 Focusing in on the location of photosynthesis in a plant

Energy Processes

Photosynthesis (Green Plants)

sunlight +water + carbon dioxide  oxygen + sugars

Respiration (All living things)

oxygen + sugars  ATP +water + carbon dioxide

53 ATP is molecular energy storage

Producers

Make their own food - photoautotrophs, chemoautotrophs

Convert inorganic materials into organic compounds

Transform energy into a form usable by living organisms

Photosynthesis

Inputs – sunlight, carbon dioxide, water

Outputs – sugars, oxygen

Transformations – radiant energy into chemical energy, inorganic carbon into organic carbon

Respiration

Inputs - sugars, oxygen

Outputs - ATP, carbon dioxide, water

Transformations – chemical energy in carbon compounds into chemical energy as ATP, organic carbon compounds into inorganic carbon compounds

Definitions 54 gross productivity – total biomass produced net productivity – total biomass produced minus amount used by organism primary productivity – productivity at 1st trophic level secondary productivity – productivity at higher trophic level gross primary productivity – rate at which producers use photosynthesis to make more biomass net primary productivity – rate at which energy for use by consumers is stored in new biomass

Distribution of World Productivity

Gross Productivity

Varies across the surface of the earth

Generally greatest productivity

In shallow waters near continents

Along coral reefs – abundant light, heat, nutrients

Where upwelling currents bring nitrogen & phosphorous to the surface

Generally lowest

In deserts & arid regions with lack of water but high temperatures

Open ocean lacking nutrients and sun only near the surface

Ocean Area vs Productivity

Effects of Depth

Net Productivity

55 Some of GPP used to stay alive, grow and reproduce

NPP is what’s left

Most NPP

Estuaries, swamps, tropical rainforests

Least NPP

Open ocean, tundra, desert

Open ocean has low NPP but its large area gives it more NPP total than anywhere else

Agricultural Land

Highly modified, maintained ecosystems

Goal is increasing NPP and biomass of crop plants

Add in water (irrigation), nutrients (fertilizer)

Nitrogen and phosphorous are most often limiting to crop growth

Despite modification NPP in agricultural land is less than many other ecosystems

Productivity Calculations

Total Primary Production = Gross Primary Production (GPP)  Amount of light energy converted into chemical energy by photosynthesis per unit time

Joules / Meter2 / year

Net Primary Production  GPP – R, or GPP – some energy used for cell respiration in the primary producers

Represents the energy storage available for the whole community of consumers

Standing crop = Total living material at a trophic level

Producers

NPP = GPP – R

56 Consumers

GSP = Food eaten – fecal losses

NSP = change in mass over time

NSP = GSP – R

Measuring Primary Production

Measure aspects of photosynthesis

In closed container measure O2 production, CO2 uptake over time

Must measure starting amount in environment then amount added by producers

Use dissolved oxygen probe or carbon dioxide sensor

Measure indirectly as biomass of plant material produced over time (only accurate over long timer periods)  this gives NPP

Light and Dark Bottle Method – for Aquatic Primary Production

Changes in dissolved oxygen used to measure GPP and NPP

Measures respiration and photosynthesis

Measure oxygen change in light and opaque bottles

Incubation period should range from 30 minutes to 24 hours

Use B.O.D. bottles

Take two sets of samples measure the initial oxygen content in each (I)

Light (L) and Dark (D) bottles are incubated in sunlight for desired time period

NPP = L – I

GPP = L – D

R = I - D 57 Sample Data

Method evaluation

Tough in unproductive waters or for short incubation times

Accuracy in these cases can be increased by using radioactive isotopes C14 of carbon

Radioactivity measured with scintillation counter

Can use satellite imaging: Nutrient rich waters of the north Atlantic

Measuring Secondary Productivity

Gross Secondary Production

Measure the mass of food intake (I) by an organism (best if controlled diet in lab)

Measure mass of waste (W) (excrement, shedding, etc.) produced

GSP = I – W

Net Secondary Production

Measure organism’s starting mass (S) and ending mass (E) for experiment duration

NSP = E-S

Method evaluation

GSP method difficult in natural conditions

Even in lab hard to get exact masses for waste

NSP method hard to document mass change in organism unless it is over a long time period

What types of things effect productivity?

What can we measure for an experiment?

58 Effects of light exposure – strength, time, color, …

Effects of temperature

Differences between types of plants

Differences between types of producers

Effects of nutrient additions

Effects of salinity

Other parameters to change

Terrestrial vs. aquatic

Oxygen, carbon dioxide

Biomass

B.O.D. bottles

GPP estimates

Problems

Problems

The GPP of the producers in the area, large rainforest trees, is 0.0050 g/cm2/day and 25% of this productivity is consumed in respiration. Calculate the NPP.

Terrestrial Biomes

IB Syllabus: 2.1.7-2.1.9

AP Syllabus

Ch 6

Video – planet Earth – pole to pole

Syllabus Statements 59 2.1.7: Define the term Biome

2.1.8: Explain the distribution, structure and relative productivity of tropical rainforests, deserts, tundra and any other biome

What is a biome?

World climate is variable

Differences in temperature and precipitation

Different climates  Different communities

Biomes = Regions of the earth characterized by specific climates and community types

Remember they cross national boundaries

Real biomes do not have sharply defined boundaries. Ecotones = Transitional zones

Biomes not uniform, mosiac of patches

Vary in microclimate, soil types, disturbances

Major Terrestrial Biomes

Desert

Tundra

Forests

Tropical Rainforest, Tropical deciduous forest

Temperate Rainforest, Temperate deciduous

Tiaga (Boreal)

Grasslands

Scrublands

Mountains

60 For each Biome you should comment in the distribution, climate (read climatograms), structure, relative productivity and limiting factors

Main Biome Effects

Vegetation changes

Plants in cold regions have traits to limit heat & water loss

Winter dormancy (drop leaves), smaller size, evergreens have needles

Plants in dry areas must lose heat and conserve water

No leaves, water storage, nocturnal activity

Plants in rainforests must get light and remove water

Broad leaves, drip tips, radiate heat

Deserts

Climate

Precipitation < 25 cm / yr – scattered unevenly through year Arid

May be Tropical, Temperate and Cold types – always extremes

High to moderate insolation

Distribution

30% of earth surface  between 30 degrees north and south of the equator – Major ones Saraha (Africa), Gobi (Asia), Mojave (N. america)

Structure

Simple – very little vegetation

Most complex is temperate desert which has largest cacti

Relative Productivity

Low – limited by water availability

61 World Distribution of Deserts

Desert Types

Tropical Deserts

High temp. year round

Little rain, only 1-2 months

Driest places on earth

Few plants

Hard windblown surface: sand & rock

Middle East areas

Desert Types

Temperate Deserts

Day temp. high in summer, low in winter

More precipitation

Sparse vegetation – suculents, cacti, animals

Southern CA (Mojave)

Desert Types

Cold deserts

Winters cold

Summers warm to hot

Precipitation low

Gobi desert, China

Plant Adaptations

Every drop of water counts

62 Wax coated leaves limit transpiration

Deep roots tap underground water

Wide spread shallow roots gather falling water

Drop leaves & dormancy in heat & dry periods

Store biomass in seeds

Animal Adaptations

Hiding in cool areas during day

Thick skin

Dry feces, concentrated urine

Water from dew & food

Dormancy in heat & drought

Human Impacts on Deserts

Temperate Grasslands

Climate

Precipitation 25-45 cm / yr – enough to grow grass, erratic Semiarid fire, drought, animals prevent tree growth

May be Tropical, Temperate

Moderate insolation

63 Distribution

9% of earth surface  Temperate Latitudes – Major onesNA tall grass prairie, steppes, pampas, veldt

Grasslands overall up to 40% of earth’s surface

Structure

Simple – grasses and herbaceous plants

Relative Productivity

Medium to high – high turnover of grasses, rich soils

World Distribution of Grasslands

Grassland Types

Temperate grasslands

Vast plains and rolling hills

Summer hot & dry

Winter cold

Sparse, uneven precipitation

Thick fertile soils

Grassland Types

Tropical Grasslands

Savannas

High average temp

Moderate rainfall

Prolonged drought

Herds of herbivores

64 Grazing & Browsing

Africa, SA, Australia

Migrations in dry season

Herbivore coexistence

Minimize competition by resource partitioning

African animals differ by region & niche

1. Giraffes eat leaves from tree tops

Elephants eat leaves and branches further down

Gazelles & Wildebeasts eat short grasses

Zebras eat longer grass & stems

Human effects on Grasslands

Tundra

Climate

Precipitation < 15 cm / yr – mostly snow & summer rain Arid

Bitter cold  -57 – 50 °C - permafrost low insolation gives short growing season

65 Distribution

60 – 75 °N latitude  – northern North America, Asia, Greenland

About 20% of the earth’s surface

Structure

Simple – low spongy mat of vegetation, lichens, mosses

Even trees are less than knee high

Relative Productivity

Low – limited by temperature and insolation

Tundra Distribution

Tundra

Treeless spongy mat of low growing plants

Common breeding area b/c predators visible

Organisms migratory

Cold & Windy & Dark

Ice & snow cover

Low precipitation but poor drainage b/c Permafrost

Forest Types

Undisturbed areas with moderate to high rainfall

Dominated by various species of trees and other vegetation

3 main types of forest – Tropical, Temperate, Boreal

World Distribution of Forests

Tropical Rainforest

66 Climate

Precipitation over 150 cm / yr – Wet – still rainy and dry seasons

Warm humid year round climate  80 °C high insolation gives short growing season

Distribution

23.5 °N to 23.5 °S latitude  – Tropic of Capricorn to Cancer

About 2% of the earth’s surface

Three chunks – S. & C. America, C. Africa, SE Asia

Structure

Complex – stratified layers

High diversity - 50-80% of terrestrial species

Relative Productivity

Highest in terrestrial system – unlimited by temperature and insolation

Tropical Rainforest

Broadleaved evergreen trees

High biological diversity, Specialized niches,

Much of animal life found in canopy layer

Stratification of life in different tree layers increases niche partitioning

Paradox  high diversity but very poor soils

Rapid recycling of nutrients

Little nutrients stay in soil most taken back into plants

Dense forest limits wind  animal pollinators

Temperate Forests

Significant seasonal changes

67 Abundant precipitation throughout year

Dominated by a few broadleaved deciduous trees

Simple structure

Thick layer of leaf litter

Once diverse, now predators gone

Boreal Forests (Tiaga)

Just below tundra

Dominated by coniferous tree species

Withstand cold, rapid growth in summer

Low temperature

Low decomposition, high soil acidity

In summer soil is waterlogged = muskegs

Human Effects on Forests

Climatograms Review

68