1. Biotic and Abiotic Influences on Ecosystems
(textbook section 2.7)

2. Today’s Goals Understand how abiotic factors affect ecosystems
Be able to describe some interactions between organisms
Describe how humans can affect these interactions

3. Limiting Factor
Any factor that restricts the size of a population or where it can live e.g. food availability, disease, predation

4. Tolerance Range
The range of abiotic conditions within which a species can live e.g. temperature, light, moisture

5. Carrying Capacity
As a population grows, it requires more food, water and space. At some point, the population reaches a maximum number of organisms that can survive. This limit is called the carrying capacity.

6. Carrying Capacity
The maximum population size of a particular species that a given ecosystem can sustain e.g. temperature, light, moisture

7. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Fire and tree cutting can remove shade and expose organisms to more light

8. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light

9. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light
Damming rivers and draining wetlands reduces water availability

10. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light
Water
Damming rivers and draining wetlands reduces water availability

11. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light
Water
Damming rivers and draining wetlands reduces water availability
Farming practices can change nutrient levels in soil

12. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light
Water
Damming rivers and draining wetlands reduces water availability
Nutrients
Farming practices can change nutrient levels in soil

13. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light
Water
Damming rivers and draining wetlands reduces water availability
Nutrients
Farming practices can change nutrient levels in soil
Global warming can reduce available habitat for cool-adapted species.

14. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Fire and tree cutting can remove shade and expose organisms to more light
Water
Damming rivers and draining wetlands reduces water availability
Nutrients
Farming practices can change nutrient levels in soil
Temperature
Global warming can reduce available habitat for cool-adapted species.

15. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Think-pair-share
Try filling out the ‘Aquatic Ecosystems’ chart on your own, then compare with a partner.

16. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths
Fertilizer runoff can increase nutrients in the water and cause algal blooms.
Pollution from burning fossil fuels increases acid rain in aquatic ecosystems
Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.
Salting highways and irrigation can increase the concentration of salt.

17. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths
Nutrients
Fertilizer runoff can increase nutrients in the water and cause algal blooms.

18. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths
Nutrients
Fertilizer runoff can increase nutrients in the water and cause algal blooms.
Acidity
Pollution from burning fossil fuels increases acid rain in aquatic ecosystems
Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.
Salting highways and irrigation can increase the concentration of salt.

19. What are some ABIOTIC factors in Ecosystems
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths
Nutrients
Fertilizer runoff can increase nutrients in the water and cause algal blooms.
Acidity
Pollution from burning fossil fuels increases acid rain in aquatic ecosystems
Temperature
Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.
Salting highways and irrigation can increase the concentration of salt.

20. Light Nutrients Salinity
What are some ABIOTIC factors in Ecosystems? How do humans affect those factors?
Key Abiotic Factor
Human action and result
Light
Activities that increase erosion or stir up bottom sediments that can reduce light at lower depths
Nutrients
Fertilizer runoff can increase nutrients in the water and cause algal blooms.
Acidity
Pollution from burning fossil fuels increases acid rain in aquatic ecosystems
Temperature
Industries release heated wastewater in to lakes and rivers, killing fish and other organisms.
Salinity
Salting highways and irrigation can increase the concentration of salt.

21. What are some ways that BIOTIC factors interact in Ecosystems?

22. 1. Competition
Two or more individuals try to get enough of one resource
It is a negative relationship because both organisms are harming each other.
Example: foxes and coyotes feed on common prey such as mice and rabbits.
Symbol: -/-

23. Competition Examples
Elephants fight each other so that the dominant elephant will get to breed with the female (intraspecific competition – within a species)
Barnacles competing for space on rocks
Frogs and lizards compete for the same insects (interspecific competition – among different species)
Trees compete for light in the forest

24. 2. Predation One predator eats and kills its prey.
Example: lynx catch, kill, and eat snowshoe hare.
Symbol: +/-

25. Predation Examples Leopard killing a buschbock (gazelle)
Venus fly trap – traps and digests flies
Gypsy moths eat leaves
Baleen whales eat plankton

26. 3. Mutualism Mutualism occurs when two individuals benefit each other
Example: a bee and a flower, seed dispersal by animals, cleaner fish
Symbol: +/+

27. Mutualism Examples Red-billed oxpecker eats insects on impala
Red-billed oxpecker eats insects on impala
Clownfish live among anemones
“Devil’s Garden”: ants poison all the plants except a single species –fending off competition and herbivory. The tree provides hollow stems for the ants to live in.

28. 4. Commensalism
Commensalism occurs when one individual benefits, the other one neither benefits nor is harmed
Example: Barnacles live on humpback whales but feed on other organisms in the water; birds building nests in trees.
Symbol: +/0

29. Commensalism Examples
Orchids and mosses make their homes on tree trunks
Cattle egrets forage in fields with livestock

30. 5. Parasitism
Parasitism is when one individual lives on or in a host organism and feeds on it
Parasites are generally smaller than their hosts
Example: tapeworms are parasites of lynxes and wolves.
Symbol: +/-

31. Parasitism Examples Botfly larvae are internal
parasites of small mammals
Strangler figs are parasites of
trees
Heartworms are parasites of dogs
Cowbirds have a form of nest parasitism

32. Summary Table Type of Interaction Sign Effects Competition -/-
Both species affected negatively
Predation
+/-
One species benefits, one species dies
Mutualism
+/+
Both species benefit
Commensalism
+/0
One species benefits, one is unaffected
Parasitism
One species benefits, one species is disadvantaged

33. Practice!
Classify each of these species interactions based on its description:
flatworms live attached to the gills of horseshoe crabs obtaining bits of food from the crabs’ meals. The crabs are unaffected.

34. Practice!
Classify each of these species interactions based on its description:
Lichens found on tree bark consist of algae and a fungus. The fungus obtains food from photosynthesis of the algae and the algae has a place to live.

35. Practice!
Classify each of these species interactions based on its description:
A flea feeds on the blood of a ground squirrel.

36. Practice!
Classify each of these species interactions based on its description:
Both bluebirds and starlings are cavity nesters (nest in holes in trees, poles, and fence posts). Neither species is able to dig holes. Both must rely on holes that already exist.

37. Practice!
Classify each of these species interactions based on its description:
A wood turtle lays its eggs on sand or gravel-sand beaches and banks along streams. A raccoon eats the turtle’s eggs.

38. Homework:
p.55 # 1,7,8