Abiotic and Biotic Factors of the Environment

UNIT 2 NOTES

ABIOTIC AND BIOTIC FACTORS OF THE ENVIRONMENT

I.  Abiotic and Biotic

·  Abiotic factors of the environment are nonliving factors, such as temperature, precipitation, rock bed, salinity, sunlight etc.

·  Biotic factors of the environment are living factors, such as predators, food sources, interspecific and intraspecific competition, parasite, disease causing agents

II.  Climate

·  Climate – the long-term prevailing weather conditions in a particular area, we are talking about long time periods

·  Weather – includes temperature, precipitation, cloud conditions, light conditions at a given time

·  Climate is determined by a wide range of factors:

1. Sun light and heat that it generates
2. Atmosphere composition
3. Surface conditions
4. Pressure
5. Wind

·  Because the Earth is a sphere, regions around the equator receive sunlight at a 90° angle, while the areas on the South and North receive the light at a lower angle. This lower angle reduces the energy that reaches these locations

·  Seasons are due to the tilted angle of the Earth’s rotational axis around the sun.

·  Ocean currents and wind patterns also influence temperature and precipitation all around the world.

·  Climate is also affected by topography. As moisture filled air moves up on high mountains, it cools down and forms droplets of water that fall as rain. However, as the air moves down the mountain, it does not bring any more moisture. So the downwind side of mountains is dry.

III.  Climate and Human Influence

·  Climate change is any change in global temperature and precipitation patterns. Earth naturally has fluctuations in these patterns over very long time periods, hundreds of thousands to millions of years.

·  Anthropogenic climate change – alterations in long-term atmospheric conditions cause by human activity. Evidence suggests that today’s climate change is so fast, it cannot be caused by natural conditions alone. It is mostly due to human activities.

·  Greenhouse gases play a major role in determining the earth’s climate. These are compounds in the atmosphere that absorb heat that radiates from the earth’s surface and reradiate it back to the surface – greenhouse effect

·  Greenhouse gases include water vapor, CO2, CH4, NO, and some other products like chlorofluorocarbons. Human activities, such as burning fossil fuels, industrial activities and agriculture increased the concentration of these gases in the atmosphere. Figure 4 and Figure 5 in Module 178.

·  Bioskill – Interpreting Graphical Data of Atmospheric CO2 Concentrations – Figures 6, 7 and 8 in Module 178

·  Consequences of the climate change:

1. Glaciers and sea ice shrink
2. Snow and sea ice melts earlier each year
3. Decreased reflection of the white snow and ice cover decreases solar radiation which increases temperature even more – positive feedback mechanism – accelerating mechanism in which the consequences push a mechanisms to go even faster
4. Increased surface temperatures
5. Changes in weather patterns and precipitation
6. Permafrost melts and releases more greenhouse gases – yet another positive feedback
7. Increased precipitation may increase erosion in some areas

Figure 9 – Module 178

IV.  Terrestrial Biomes

·  Biome – a large geographical area that contains a unique collection of naturally occurring animals and plants. Biomes are categorized as aquatic and land biomes.

You need to understand how climate and other factors influence biomes and how their biodiversity can be useful for us.

Figure 2 – Module 179

·  Main environmental factors that determine the nature of a biome are average yearly temperature (°C) and the annual precipitation (cm). These are the most important abiotic factors of terrestrial biomes.

·  Forest biomes usually require substantially more yearly precipitation than grassland biomes.

·  Higher annual temperatures with lower precipitation can lead to deserts, while very low temperatures result in tundras.

·  Climatographs are used to show the temperature and precipitation in a given are broken down by month.

·  Major human activities such as deforestation, overwatering and habitat destruction endangers terrestrial biomes.

Figure 6 – Module 179

V.  Aquatic Biomes

·  Aquatic biomes are divided into two major types: freshwater and marine biomes.

·  They make up about 3/4th of the earth’s surface.

·  They are interconnected with the terrestrial biomes because of the water cycle.

·  Most important abiotic factors in aquatic biomes:

o  Salinity – salt content (fresh water, brackish water, salt water, brine)

o  Nutrient content (oligotrophic water, eutrophic water)

o  Light intensity (photic and aphotic zones)

o  Temperature stratification (thermocline)

o  Bottom surface (benthic zone)

Figure 4 – Module 179 as an introduction to the case study.

As a conclusion of the case study:

Many abiotic factors can interact to cause various changes in the environment. For example, oxygen concentration can be depleted in aquatic biomes by warming water, increased number of decomposers that use up the oxygen, increased salinity, less turbulence and too high nutrient concentration.

Eutrophication – a dangerous condition in both fresh water and marine biomes. Because of increased nutrient wash off from farms and possibly sewage from cities, aquatic biomes become eutrophic. Algae and bacteria can reproduce at a higher pace by using the nutrients from the wash off. The consequences:

·  Higher number of heterotroph bacteria use up the oxygen in the water

·  Algae and bacteria cover the surface of the water so photosynthetic organisms in the water don’t get sunlight and die

·  Toxins are produced by certain algae and bacteria that can harm other living organisms in the water

·  Higher number of dead organisms increase the number of decomposing organisms and they also use up the oxygen in the water

POPULATIONS

I.  Human Population Growth

·  Populations can increase their numbers by the following:

o  Increasing birth rate

o  Decreasing death rate

o  Increasing immigration and/or decreasing emigration

·  Due to better healthcare, humans live longer today than ever before in human history. As a consequence, human population exploded since the nineteenth century.

Data analysis – 7 Billion and Counting, Nature

http://www.pbs.org/wgbh/nova/worldbalance/numb-nf.html -- human populations over time

II.  Estimating Populations:

·  Population ecology studies the number, composition, growth rate, dispersion and environmental factors of populations.

·  Populations: all living organisms that belong to the same species and live in the same area.

·  The number of organisms in a population can be estimated or calculated by using:

o  Density – number of organisms per unit area or per volume. Fairly constant density over time is an indication of a healthy population.

o  Dispersion – The changes of density of a population across its range. Can be clumped (herds of grazing animals or schools of fish grouping around a food source), uniform (creosote bushes in the desert because of the limited water supply, artificially planted farm trees in an orchard), random (usually for no particular reason, birds flying in the wind or insects flying, weeds as their seeds were dispersed)

o  Demography – calculations to account for the birth, death rate and immigration and emigration data. Life tables or survivorship curves are used to describe the demography of populations. Survivorship curves show how mortality varies with age of the individuals in a population. Type I survivorship – organisms rarely die when young, parents take care of their young and organisms tend to die in large numbers when old. Type II survivorship – organisms have an equal chance of dying when young or old. Type III survivorship – organisms die in an early age but the ones that survive, can live for a long time.

Figure 3 and Table 3 in 182

III.  Growth of Populations Over Time

·  Death, birth, immigration and emigration changes population numbers.

·  The number of organisms in a population will be limited by various environmental factors, such as food, nesting place, water supply etc. The maximum number of individuals an environment can support over time is called its carrying capacity (K).

·  Exponential growth is where the growth rate increases exponentially. This is due to having plenty of resources available for all new organisms. How many new organisms are added into the population by each already present organism in a given time period is called the per capita increase (rmax), this multiplied by the population size (N), gives us the population growth or decline over time (G). G = r(max) N (G can also be represented by dN/dt)

·  Logistic growth is when the resources start to limit the growth of the population because the carrying capacity of the environment is reached by the individuals in the population. As the population size (N) gets larger, the per capita increase (rmax ) gets smaller, because fewer offspring are born or can survive. In this case, G=rmax N (K-N/K) (G can also be represented by dN/dt) In this case, r = rmax (K-N/K)

IV.  K and r Selection

·  Evolution of populations developed different ways of dealing with the varying carrying capacity of the environment.

·  K selection is a process in which organisms produce fewer offspring, later in their lives because the environment cannot support many new offspring. These organisms care for their young.

·  r selection is a process in which organisms produce lots of offspring, reproduce fast, from a young age but do not care for their young. These organisms have a different strategy to assure reproductive success.

Think back to evolutionary fitness. The goal is to reproduce

V.  Factors that Regulate Population Size

·  Once the carrying capacity of the population is reached, various environmental factors will limit the number of organisms in the population – density-dependent factors affect the population only at certain densities. Examples of these are food sources, water sources, nesting place, spread of disease causing agents, etc.

·  Density-independent factors impact the population regardless of its density. Examples: weather conditions, volcanic eruption etc.

·  Because these conditions change over time and the carrying capacity of the environment can change with it, population numbers fluctuate greatly over time.

Figures 8 and 9 Module 181

http://www.pbs.org/wgbh/nova/earth/global-population-growth.html

http://www.youtube.com/watch?v=sc4HxPxNrZ0 – 7 billion

Figures 19 and 21 in Module 181

VI.  Evolution of Life History Strategies

·  Each species confronts a trade-off between parental investment and the number of offspring it produces. Some species may have only a few offspring and takes good care of them (great investment), while others may have many offspring but invest little energy into taking care of them. Each strategy has its advantages and drawbacks.

·  Most species has a life history strategy that is in between the two extremes.

Complete the case study on Population Dynamics and the concept map

COMMUNITIES – SPECIES INTERACTIONS

I.  Introduction

·  Communities – all living organisms in a given area that interact with each other. This interaction can be two basic types:

1. Intraspecific interaction – the interacting organisms belong to the same species
2. Interspecific interaction – the interacting organisms belong to different species

·  Ecological Niche – Every species has a determined set of behaviors, resources and environmental factors that they can tolerate. Fundamental niche describes all limiting factors and resources that a species can possibly utilize. Realized niche describes all factors that it does utilize in the presence of biotic interactions with competitors and predators.

II.  Interspecific Interactions

·  There is a wide range of interactions between species. The following list shows the most common types (+ means beneficial interaction, - means harmful interaction, 0 means neutral or no interaction):

1. Competition (-,-) because it is harmful for both parties, competition limits the number of individuals in each population and also drives evolutionary fitness because the organisms of the two parties compete with each other for resources. (Ex. Plants competing with other plants for sunlight in a forest, zebras and antelopes compete for grass on the savannah). Figure 2 – Module 185. Competitive exclusion principle states that in a community, where two species compete for the same limiting factors, they cannot coexist and only one species will survive. If two species compete with each other for the same resources, they may be forced to divide up the available resources with each other – resource partitioning. In this case, evolution may benefit organisms that have more different traits from the competition.
2. Predation, herbivory, parasitism (+,-) – feeding relationships, where one organism benefits by consuming the other organism or its parts. However, these relationships can also be beneficial for the entire ecosystem, when for example herbivores are controlled by predators, so plants can survive. Coevolution of both parties is also very powerful. List some adaptations below of each party:

Adaptations of predators / Adaptations of prey / Adaptations of plants / Adaptations of herbivores / Adaptations of parasites / Adaptations of hosts
Enhancement of senses, agility, sharp teeth, claws, strong muscles, bones / Forming packs, playing dead, warning signals (behavioral adaptations), cryptic coloration (camouflage), warning coloration, toxins, unpleasant taste,
Mimicry (Batesian – harmless copies harmful, Mullerian—harmful and harmful look similar) / Toxins, thorns, unpleasant taste, fast growth, / Modified digestive system, strong teeth, tough lips, long legs and necks to reach trees, resistance to toxins / Behavioral – parasitic wasps, social parasitism – cuckoos,
Structural—resistance to stomach acid and enzymes by forming thick outer covering,
Fast reproduction / Immune response against the parasite, acids and digestive enzymes against parasites in the digestive system

The following relationships are all considered symbiotic relationships – a relationship between two species that live in intimate contact.

1. Amensalism (-,0) occurs, when one species inadvertently harms another. Usually occurs when a metabolic waste is secreted by one organism that is harmful for another (break mold secretes penicillin, that harms bacteria but does not directly benefit the bread mold either)
2. Mutualism (+,+) Sometimes mutualistic relationships are obligate, neither party can survive without the other, but sometimes facultative, they can survive without each other but they are both better off with each other. (Termites and wood digesting protists in their digestive system – obligate, clownfish and sea anemones – facultative).
3. Commensalism (+/0) Includes organisms that use another one for transportation (mites sitting on a beetle)

III.  Dominant and Keystone Species