1. Interactions in the ecosystem
Chapter Five

2. Habitats and niches I can describe the concept of the niche.
I can examine how interactions between a species and its environment define the species’ niche.

3. Habitats and niches
An ecosystem is a network of living and nonliving things.
Organisms are connected by food webs and common needs.
Each species has its own way of gathering resources from the environment.

4. Habitats and niches Ecosystems can be very large.
The environment may be different in one part of the ecosystem from another part of the ecosystem.
For example, near a stream versus on a dry hill above the stream.
Organisms in each part are different from each other.

5. Habitats and niches
Each organism is adapted to the conditions in its part of the environment.
Each habitat is different; they can be small or large, wet or dry, and vary depending on the size of the organism.

6. Habitats and niches Each organism is adapted to life in its habitat.
It has its own way of gathering food, reproducing, and avoiding predators.
The role of an organism in its ecosystem is called its niche.

7. Habitats and niches
A niche is more than just the habitat, it includes what an organism does in the habitat.
Niches include both biotic and abiotic factors.
Factors that contribute to niches: food sources, predators, temperature, sunlight, water, and time of day.

9. Habitats and niches
All members of a species are adapted to the same niche.
No two species can share the same niche in the same habitat.
They can occupy niches that are similar.

10. Habitats and niches 2 species, similar niche: Anolis lizards
In the tropics, anolis lizards occupy a similar niche.
Large jawed anolis eat large insects
Small jawed anolis eat small insects
They can live side by side because they occupy different niches.

11. Habitats and niches
If two species try to occupy the same niche in the same habitat they will compete for resources.
If they try to compete, the species better at getting the food, shelter, etc. will survive and the other species must either find another habitat or die out.

12. Habitats and niches
The extinction of a species due to direct competition with another species for a resource is called competitive exclusion.
This refers to the extinction in one location, not the extinction of the entire species everywhere.

13. Habitats and niches
Often the activities of one species can affect another species niche.
For example, two species of barnacles.
Both live on rocks in the surf zone of the ocean.

14. Habitats and niches
Species B lives low on rocks usually covered by water.
Species A lives on rocks usually exposed to the air.
Species B is vulnerable to drying out, while species A is more resistant to drying out.

15. Habitats and niches
If species B were removed, species A would move down and occupy the area that B used to cover.
However, as long as species B was around, species A was pushed out and up to the drier rocks.
It was discovered that the niche of one species could affect the niche of another.
The presence of one species might limit the niche of another, just like the barnacles.

16. Habitats and niches
The theoretical niche of an organism is called its fundamental niche.
Where the organism could live.
The niche than an organism actually used is called its realized niche.
Where the organism actually lives.

17. Habitats and niches
Niche diversity, or the number of niches in an ecosystem is determined by abiotic factors.
Factors such as moisture and temperature.

18. Habitats and niches
A predator is an organism that actively hunts other organisms.
The hunted organism is the prey.
Predators play an important role in niche diversity by decreasing the population of the prey species.

19. Habitats and niches
If a predator reduces the population of one species, more resources will become available for another species.
The action of the predator can therefore, create another niche.
Why do we have hunting season in MI right before Winter?

20. Habitats and niches
Robert Paine showed how predators help to form niches.
Paine removed the dominant predator, a sea star, from several tide pools.
Then number of mussels increased until the mussels were the dominate species.
Without the sea stars, the number of species in the tide pools reduced from 15 to 8.

21. Habitats and niches
A predator that promotes niche diversity, such as the sea star, is called a keystone predator.
Another example is the sea star, crown of thorns, in the Great Barrier Reef.
Humans have removed the predatory fish, and now the crown of thorns removes large stretches of the reef each year.
This results in less reef, less habitats, and lower diversity in the ecosystem.

22. Evolution and adaptation
I can explain how a species adapts to its niche.
I can describe convergent evolution and coevolution, and relate each to the concept of the niche.

23. Evolution and adaptation
Ecosystems change over time.
A change in the environment will affect the niches of the organisms in that environment.
If a niche disappears, the species may become extinct.
Changes in the environment affect the evolution of populations.

24. Evolution and adaptation
Evolution is a change in a species over time.
Evolution happens when some individuals have genetic variations that allow them to produce more offspring than other members of the population.
Over time these variations are passed down through generations.
Natural selection for advantageous traits eventually changes the whole population.

25. Evolution and adaptation
Evolution causes populations to adapt to specific niches.
This reduces competition with other species.
Example: Warblers in the NE U.S.
All 5 species of warblers feed on insects in the branches of spruce trees.

26. Evolution and adaptation
Although, the warblers may seem to compete with each other, each species gets its food from a different section of the spruce tree.
This allows all 5 species to coexist.
Ecologists call a species with a small niche, a specialized species.
A koala is another example.

27. Evolution and adaptation
Koalas feed exclusively on the leaves of eucalyptus trees.
Specialized species are vulnerable to extinction; a single environmental change can eliminate their niche.
If eucalyptus were no longer able to grow in their niche, koalas would go extinct.

28. Evolution and adaptation
Ecologists call a species with a wide niche a generalized species.
Generalized species have alternate food sources and can live in a variety of environments.
Mice and cockroaches are generalized species.
They can change their behaviors easily.

29. Evolution and adaptation
Similar ecosystems often have similar niches.
Similar ecosystems provide similar opportunities for different organisms.
If niches in two ecosystems are similar, the organisms the evolve there may also look alike.

30. Evolution and adaptation
The independent development of similar adaptations in two species with similar niches is called convergent evolution.

31. Evolution and adaptation
The wings of birds and bats are an example of convergent evolution.
Birds and mammals are different types of animals, and the bird and bat evolved flight separately.
Both the bird and the bat evolved wings as an adaptation to a niche that required flying.

32. Evolution and adaptation
Another example of convergent evolution is the dolphin and the ichthyosaur, and extinct reptile from the Jurassic period.
The animals share adaptations to life in water, such as fins, streamlined shape, nostrils on top of their heads and long noses.

33. Evolution and adaptation
Other species in an environment are also important to organisms.
Remember keystone predators can help make an ecosystem more diverse.
Evolution results in species whose niches are different enough to limit competition.

34. Evolution and adaptation
Organisms that live closely together and interact may have evolutionary responses to each other.
Species that interact closely may become adapted to one another by a process called coevolution.

35. Evolution and adaptation
Coevolution can occur as a result of feeding relationships.
One example is plants and caterpillars.
Plants adapted to produce poisonous chemicals, but caterpillars adapted to be able to withstand the chemicals.
Caterpillars became able to eat plants other animals could not.

36. Evolution and adaptation
Species can also have adaptations that exist to their mutual benefit.
The acacia tree in South America have coevolved with insects.
The trees have large, hallow thorns that provide nests for stinging ants. The only place the ants can nest and the only food source for the ants, also.

37. Evolution and adaptation
The acacia tree benefits from the ants, too.
The ants attack any animal landing on the tree and clear vegetation surrounding the tree.
Research has shown the tree cannot survive without the ants, and the ants without the tree.
They are totally dependent on each other.

38. populations I can explain how populations of organisms grow.
I can describe the factors that limit the growth of a population.
I can identify the shapes of growth curves that represent populations of different organisms.

39. populations
The biotic and abiotic factors that define a niche also limit a species growth.
For example, availability of food can limit the size of a population.

40. populations
1798 Thomas Malthus observed that the human population can quickly out grow the environments ability to support it.
However, Malthus thought that humans suffered from famine and disease when the population became too large.
This made an impression on Charles Darwin.

41. populations
The idea that organisms produce more offspring than can survive was important to Darwin’s theory of evolution.
Overproduction causes competition for resources, which in turn causes the selection of the most favorable adaptations (survival of the fittest).

42. populations
Any population has the ability to increase exponentially if it has a perfect environment.
Exponential growth is population growth in which the rate of growth in each generation is a multiple of the previous generation.
In reality, conditions are never perfect.
Limited resources and area restrict pop. growth

43. populations As a population grows, it takes more habitat.
Resources become scarce.
Individuals have to compete.
The death rate rises.
The birth rate decreases due to declining resources

44. populations The growth of the population slows, then ceases.
The number of births will equal the number of deaths.
The total number of individuals in a species that can be supported by an ecosystem is called the carrying capacity for that species.

45. populations
A classroom can be thought of as having a carrying capacity.
What would limit the carrying capacity of this classroom?

46. populations
An s-shaped curve can represent the change in size of a species.
The population starts out small, and then increases rapidly, and exponentially. When it reaches its carrying capacity growth slows.

47. populations
Many populations stop growing when they reach their carrying capacity.
The forces that slow the growth of a population are called limiting factors.
Examples of limiting factors: climate, predation, parasitism, disease, space, water, humans, disasters, and food availability.

48. populations There are two kinds of limiting factors:
Density dependent limiting factors
Density independent limiting factors

49. populations
Density dependent limiting factors are limiting factors that are dependent on population size.
For example, food supply, predation, and disease.
These factors are related to competition and interactions between organisms.

50. populations
As the population grows, density dependent limiting factors act more strongly to limit growth.

51. populations
Some factors limit a populations growth regardless of the populations size.
For example, a hurricane, fires, temperatures, or rainfall.
A limiting factor that affects the same percentage of a population regardless of its size is called a density independent limiting factor.

52. populations
Density independent limiting factor populations show a “boom-and-bust” growth curve.
A boom-and-bust curve represents a population whose size grows exponentially during favorable conditions and then collapses when conditions change.
Insect populations often follow this pattern.

53. The human population
The growth curve of the human population has long been an exponential curve.
This is possible because of advances in agriculture, technology, energy development, transportation, and medicine.
No population can grow this way forever, though.

54. The human population
The growth of the human population on Earth must level off as the planet’s resources become fully utilized.
The challenges for the human species lie in minimizing our impact on our only habitat: Earth’s biosphere.