Ecosystem Interactions and Populations

Interactions and Populations All populations of species in an ecosystem strive for survival All populations of species in an ecosystem strive for survival What do you think populations need in order to survive? What do you think populations need in order to survive? Resources: food, water, safe shelter Resources: food, water, safe shelter But there are many factors that affect a population’s survival But there are many factors that affect a population’s survival

Biotic and Abiotic Interactions Biotic Interactions: Interactions between living things. Biotic Interactions: Interactions between living things. Example: How would a flower and a bee interact? How would a moose and a parasite interact? Example: How would a flower and a bee interact? How would a moose and a parasite interact? Abiotic Interactions: Interactions between living and non-living things Abiotic Interactions: Interactions between living and non-living things Example: How would a deer be affected by a dry and hot weather? Example: How would a deer be affected by a dry and hot weather?

Biotic Interactions There are three main ways in which organisms in communities interact with each other. There are three main ways in which organisms in communities interact with each other. 1) Competition: interactions between two or more organisms competing for the competing for the same resource same resource in a given habitat. in a given habitat.

Biotic Interactions 2) Predation: the act of one organism eating another organism in order to obtain food. Prey animals adapt in order to avoid being eaten. Ex. Camouflage or the ability to run very fast. - Mimicracy: one species that looks like another species.

Biotic Interactions 3) Symbiosis: a close interaction between two different species where one species lives in, on, or near another species. Three types of Symbiosis: a) Mutualism b) Commensalism c) Parasitism What do you think each of these mean?

Biotic Interactions Mutualism – both species benefit from the partnership. Ex: the boxer crab carries around anemones in its claws. The anemone protects the boxer crab from predators, and the anemone eats scraps of food that the boxer crab drops. Mutualism – both species benefit from the partnership. Ex: the boxer crab carries around anemones in its claws. The anemone protects the boxer crab from predators, and the anemone eats scraps of food that the boxer crab drops. Commensalism – one species benefits from another species, but that species gets no harm or benefit from it. Ex. A bird building a nest in a tree (tree doesn’t suffer) Commensalism – one species benefits from another species, but that species gets no harm or benefit from it. Ex. A bird building a nest in a tree (tree doesn’t suffer) Parasitism – one species benefits at the expense of another. Ex. Leach or a tick sucking blood from an animal. Parasitism – one species benefits at the expense of another. Ex. Leach or a tick sucking blood from an animal. SEE PAGE 47 for MORE EXAMPLES SEE PAGE 47 for MORE EXAMPLES

Which type of Symbiosis? 1 2 3

Image 1 – parasitic tick on a dog Image 1 – parasitic tick on a dog Image 2 - As buffalo eats grass, the egrets (birds) eat the insects that they stir up. The buffalo is unaffected. Image 2 - As buffalo eats grass, the egrets (birds) eat the insects that they stir up. The buffalo is unaffected. Image 3 – The bee feeds from the flower’s nectar, but it also helps cross-pollenate the flower so it can reproduce. Image 3 – The bee feeds from the flower’s nectar, but it also helps cross-pollenate the flower so it can reproduce.

Birth of an Ecosystem: Surtsey, Iceland Read pp Read pp

Characteristics of Populations Populations are always reproducing. Populations are always reproducing. As there are more and more of an organism in one given area, they each get a smaller share of the total resources in that area. As there are more and more of an organism in one given area, they each get a smaller share of the total resources in that area. Equilibrium – when the number of births in a population equals the number of deaths. (No growth or shrinkage of the population) Equilibrium – when the number of births in a population equals the number of deaths. (No growth or shrinkage of the population) Carrying capacity – The maximum number of individuals that an ecosystem can support without reducing its ability to support future generations of the same species. Carrying capacity – The maximum number of individuals that an ecosystem can support without reducing its ability to support future generations of the same species.

Equilibrium and Carrying Capacity In this graph, the rabbit population has achieved equilibrium, and the population remains constantly below the ecosystem’s carrying capacity However, populations in ecosystems often goes in cycles.

Snowshoe Hare and Lynx Populations

Predator-Prey relationship Snowshoe hares are prey for the lynx Snowshoe hares are prey for the lynx As the population of hares increases, the lynx have more food, so their population increases. As the population of hares increases, the lynx have more food, so their population increases. This results in fewer snowshoe hares, because the lynx eat the hares. This results in fewer snowshoe hares, because the lynx eat the hares. Because there are so many lynx eating hares, the hares numbers decrease. Because there are so many lynx eating hares, the hares numbers decrease. There is now a food shortage for the lynx, so the weaker lynx will become malnourished, some will die – resulting in a smaller lynx population. There is now a food shortage for the lynx, so the weaker lynx will become malnourished, some will die – resulting in a smaller lynx population. Since there are less lynx, the hares population begins to increase again. Since there are less lynx, the hares population begins to increase again. This cycle will repeat itself This cycle will repeat itself

Carrying Capacity Look at the snowshoe hare population. Look at the snowshoe hare population. Which number seems to be the most common “peak”? Which number seems to be the most common “peak”? About 6000 About 6000 Therefore, 6000 is their carrying capacity. Therefore, 6000 is their carrying capacity. If they go over 6000, more lynx will come along and eat them, causing their population to dip low again If they go over 6000, more lynx will come along and eat them, causing their population to dip low again

Carrying Capacity Look at the lynx population Look at the lynx population Which number seems to be the most common peak? Which number seems to be the most common peak? About 4000 About 4000 Therefore, 4000 is their carrying capacity. Therefore, 4000 is their carrying capacity. If they go over 4000, there is too much competition and they run out of food. If they go over 4000, there is too much competition and they run out of food. Their population consequently dips Their population consequently dips

Predator-Prey relationships If an ecosystem gets overpopulated, this will exceed the carrying capacity. If an ecosystem gets overpopulated, this will exceed the carrying capacity. Predator-Prey relationships are one way to ensure that ecosystems do not get overpopulated with one species. It’s a natural form of population control. Predator-Prey relationships are one way to ensure that ecosystems do not get overpopulated with one species. It’s a natural form of population control. If there is too much prey, there will be more predators to eat them If there is too much prey, there will be more predators to eat them If there are too many predators, they will compete and run out of prey If there are too many predators, they will compete and run out of prey

Limiting Factors

Limiting factors are any environmental factor that prevents an increase in the number of organisms. Limiting factors are any environmental factor that prevents an increase in the number of organisms. Biotic Limiting Factors Biotic Limiting Factors Competition among organisms for resources, presence of predators, reliance on other organisms for survival, presence of disease. Competition among organisms for resources, presence of predators, reliance on other organisms for survival, presence of disease. Abiotic Limiting Factors Abiotic Limiting Factors Amount of sunlight, water, soil, air. Amount of sunlight, water, soil, air. Natural disturbances – storms, fires, drought Natural disturbances – storms, fires, drought Humans: e.g. logging Humans: e.g. logging

Limiting Factors Limiting Factors is what affects the ecosystem’s carrying capacity Limiting Factors is what affects the ecosystem’s carrying capacity This can cause a population to increase and decrease over the years This can cause a population to increase and decrease over the years A population cannot continue to survive over the its carrying capacity. This is unsustainable. If there are no more resources, the future generation can’t survive. A population cannot continue to survive over the its carrying capacity. This is unsustainable. If there are no more resources, the future generation can’t survive. Do you think this concept applies to humans too? Give an example. Do you think this concept applies to humans too? Give an example.

When a population cannot survive In a sustainable ecosystem, populations reach their carrying capacity and can continue to survive indefinitely In a sustainable ecosystem, populations reach their carrying capacity and can continue to survive indefinitely However, limiting factors can wipe out an entire population of a species in a ecosystem. Humans are largely responsible for this. However, limiting factors can wipe out an entire population of a species in a ecosystem. Humans are largely responsible for this.

What happens to a population that can’t survive? In a case of a major disturbance, a population can go to ZERO in an ecosystem. This happens 2 ways: In a case of a major disturbance, a population can go to ZERO in an ecosystem. This happens 2 ways: Extirpation: If a population cannot survive in one ecosystem, but it may continue to survive in another ecosystem. Extirpation: If a population cannot survive in one ecosystem, but it may continue to survive in another ecosystem. Extinction: If a population is extirpated from one ecosystem and cannot survive in any other ecosystem, it ceases to exist. The species is gone forever. Extinction: If a population is extirpated from one ecosystem and cannot survive in any other ecosystem, it ceases to exist. The species is gone forever.

Examples Extirpated: Bison Extinct: Golden toad

Homework Page 42 Questions 1 – 3 Page 42 Questions 1 – 3 Page 46 Questions 2 -8 (graph not necessary for #8) Page 46 Questions 2 -8 (graph not necessary for #8)