Grade 11 Environmental Science Unit 2 Ecology

Grade 9 Academic Science – Sustainable Ecosystems Introducing Ecosystems Section 2.2 Pages 32-35

Ecosystem  All the living organisms and their physical and chemical environment

Sustainable Ecosystem  An ecosystem that is naturally maintained

Sustainability  Ability to maintain an ecological balance

Task  Complete “Try This – Ecosystems ABCs” on Page 33  Read the following information and, using your textbook and understanding, answer the questions

Operation Cat Drop Ecology is the science of the interactions of organisms in their natural environment. This field of study developed as the impacts of humankind’s activities on the environment appeared. It became apparent that there was a need to understand the interconnections that link the various forms of life in even “simple ecological settings” such as a pond or desert area.

One of the most often-told events involves a situation in Borneo. In the early 1950s, there was an outbreak of malaria in Borneo. The World Health Organization (WHO) tried sprayed DDT to kill the mosquitoes that carried the malaria. The mosquitoes died and there was less malaria. However, there were side effects.  The thatched roofs of houses began to fall down. It turned out that the DDT was also killing a parasitic wasp that ate thatch-eating caterpillars. Cheng (1963) noted that thatched roofs on buildings in the DDT spray zone collapsed soon after spraying. He suggested the small chalcid wasp, a parasite of local moth, was highly susceptible to the DDT. As the population of wasp declined, there was a subsequent increase in moth numbers. Without the wasps to eat them, there were more and more thatch-eating caterpillars. The moths consumed and destroyed the thatched roofs.

 The insects killed by DDT were eaten by gecko lizards. The gecko became weak and slow. They became easy prey for cats. The cats died. Rats flourished. Rats carry disease, and soon, the people were threatened by outbreaks of two new serious diseases carried by the rats: sylvatic plague and typhus.  Mosquitoes are a very resilient organism, and they evolve resistance extremely rapidly. Within three generations, the mosquito population was DDT resistant.

 To cope with the problems, WHO had to parachute 14,000 live cats into Borneo to control the rat population. The program was called “Operation Catdrop” (Buckallew, 2004; Conway, 1972).

Task 1. Why did all these events occur together? Write a paragraph explaining your ideas.

2. In the context of Sustainable Ecosystems, why is this issue important to understand?

DDT stands for dichlorodephenyltrichloroethane. DDT is a chlorinated hydrocarbon with a half-life of 15 years. If you use 100 kg of DDT, it will break down as follows:

Year Amount Remaining (kg) 0 100 15 50 30 25 45 12.5 60 6.25 75 3.13 90 1.56 105 0.78 120 0.39

After 100 years, there is about 1 kg of DDT in the environment. DDT has rather low toxicity to humans, but a very high toxicity to insects, hence its use as an insecticide. Because it could be safely handled by humans, it was extensively used in WW II to reduce mosquito populations and thus control malaria in areas where US troops were fighting. After the war, DDT became popular to protect crops as well. It was overused, and soon led to the discovery of (1) insect resistance to pesticides and (2) bioaccumulation, bioconcentration and biomagnification (Madar, 1996).

Literature Cited  Buckallew, Robin. 2004. The Day it Rained Cats. (Online) Available: http://www.faulkingtruth.com/cgi-bin/Printable.cgi?GlobalWarning&1009

 Cheng FY. 1963. Deterioration of thatch roofs by moth larvae after house spraying in the course of a malaria eradication programme in North Borneo. Bulletin of the World Health Organization. 28:136-7.

 Conway GR. 1972. Ecological aspects of pest control in Malaysia. In The Record of the Conference on the Ecological Aspects of International Development, (Farrar MT, Milton JP eds.) Washington University, December 8-11, 1968, The Natural History Press, Garden City.

 Mader, Sylvia S. 1996. Biology - 5th Ed. WCB

So, what is an ecosystem?  It is all the different organisms living in an area, their interactions and the impact of the physical environment on the organisms. Note: ecosystems do NOT have clear boundaries although we tend to think of ecosystems as separate and distinct (e.g., desert ecosystem, pond ecosystem).  In other words, an ecosystem is composed of both biotic (living) and abiotic (non-living) factors. In the table below, list some biotic and abiotic factors. Biotic Abiotic

Living things within an ecosystem are organized or classified. In your own words, define the following terms and organize the terms from “smallest” to “largest” grouping. Term Definition Your Order Organism

Ecosystem

Community

Species

Population

Biosphere

What part of an ecosystem is NOT part of a community?

All an organism’s relationships with its environment – both living and non-living – make up the organism’s NICHE. An organism’s NICHE is its way of life. The place an organism lives is its HABITAT.

HOW DO SPECIES INTERACT? The most recognizable interaction is a Predator-Prey Relationship.

This relationship influences the evolution of the predator and prey. That is, traits that enhance a predator's ability to find and capture prey will be selected for in the predator, while traits that enhance the prey's ability to avoid being eaten will be selected for in the prey. The predator kills and eats the pre, while the prey tries to avoid the predator.  In the absence of prey, what describes the RATE of change in the predator population?  How might the rate of change in the predator population be altered if prey were present?  Without predators, what initially will happen with the prey population?  The graph is a typical Predator-Prey Relationship graph. What is your interpretation? Provide three observations.  Why is there more prey than predators?  What do you think Carrying Capacity is? Biotic and Abiotic Factors

Why do zebras only live on the grasslands of Africa? Why do Black Bears in North America live in temperate forests? Why do only find cacti in deserts? It is because of factors that restrict the size of a population called LIMITING FACTORS. The factors are BIOTIC and ABIOTIC FACTORS.

 BIOTIC FACTORS are living things. It is the way living things interact or relate to one another. Plants, animals and bacteria are all biotic factors.  ABIOTIC FACTORS are non-living physical and chemical components of an ecosystem (e.g., temperature, wind, snow).

ABIOTIC FACTORS Each species can survive within a range of the abiotic factors. This is called TOLERANCE RANGE. The graph shows tolerance. For example, we would find large numbers of zebras on the Africa grasslands (Area of greatest abundance). If we move away from the grassland to desert or tropical rainforest, population numbers decrease until there are zero zebras. Why? It may be that zebras cannot live in extremely hot temperatures (i.e., desert) or very wet conditions (i.e., rainforest). NOTE: Each species has its own Tolerance Range. That is, some species live in very specific conditions (i.e., small or narrow Tolerance Range) while other species can live in a wide variety of conditions (i.e., large or wide Tolerance Range).

For the following table, identify why you think these factors are Abiotic Factors. Ecosystem Abiotic Factor Your Reason Aquatic Light availability

Acidity of the water

Water Temperature

Salinity (salt levels in the water)

Nutrient availability BIOTIC FACTORS Abiotic Factors may influence WHERE organisms live, while Biotic Factors can determine HOW successful organisms can survive. For example, wolves hunt…and thus survive…more effectively in packs. This relationship is a Biotic Factor.

Biotic Factors are the interactions between individuals

Complete the following table with an EXAMPLE supporting the relationships of Biotic Factors Relationship Definition Description Your Example Competition Two individuals fighting for the same resource - - Predation One individual kills and eats another organism. One benefits while the other is harmed + - Mutualism Two individuals that live together and both benefit from the relationship + + Parasitism One organism lives and feeds on a HOST organism. The parasite benefits but the host is + - harmed Commensalism One individual benefits from the relationship while the other organism neither benefits or is + O harmed

As the size of a population grows, the demand for resources (e.g., food, space, water, shelter) also increases. Eventually, there will not be enough resources to share so all individuals survive. This is called CARRYING CAPACITY. It is the maximum population size of a particular species that an ecosystem can sustain indefinitely.

PRACTICE QUESTIONS 1. List three Abiotic Factors that are important to a land (terrestrial) ecosystem. Provide your explanation for each factor identified.

2. Provide an example of parasitism and mutualism

3. Are Abiotic Factors less important than Biotic Factors? Explain your idea.

4. Canada’s Arctic is extremely cold. List three adaptations on the body of a polar bear that allow it to thrive in the Arctic.

Homework  Page 35, Questions 1-2, 4-5, 7 ANSWERS

 In other words, an ecosystem is composed of both biotic (living) and abiotic (non-living) factors. In the table below, list some biotic and abiotic factors. Biotic Abiotic Animals Temperature and sunlight Plants Water supply Microorganisms Mineral nutrients Wind Humidity

Living things within an ecosystem are organized or classified. In your own words, define the following terms and organize the terms from “smallest” to “largest” grouping. Term Definition Your Order Organism One individual living thing. 1 Ecosystem All the different organisms living in an area, their interactions and the impact 5 of the physical environment on the organisms. Community A group of interacting populations of different species 4 Species A group of organisms able to produce fertile offspring and share common 2 genes. Thus, species resemble each other. Population A group of individuals of the same species living in a particular area. 3 Biosphere The regions of the surface and atmosphere of the Earth where living 6 organisms exist