1. 4.2 – Niches and Community Interactions
4.2 – Niches and Community Interactions
Notes – be sure to understand definitions and have a few examples to describe each concept

2. I. Niche A niche is the role that an organism plays in an ecosystem
Includes physical factors (abiotic)
*Ex:
C. And biological factors (biotic)
D. Includes how the species uses these factors to survive and reproduce
Analogy of a niche: the role of your favorite sports player on their team – needs “resources”, “habitat”

3. II. Resources and Tolerance
Resource is any necessity of life (Ex: water, food, shelter, place to feed, place to build nests or raise young)
Tolerance is the range of environmental conditions a species needs to survive and reproduce (Ex: temp., sunlight)
Tolerance determines how WELL we deal with the LACK of resources

4. III. Tolerance Example Humans can tolerate a wide range of temp
Body temps as low as 75 degrees F
As high as 105 degrees F
Optimal range is a few degrees cooler or warmer than 98.6 degrees F
The further from optimal range, the more stress it causes the individual, and lowers ability to survive and reproduce

5. IV. Tolerance determines Habitat
Habitat is the general place where an organism lives
Determined by how much tolerance the organism has to live in that habitat and still be able to survive and reproduce
Ex: temp, access to food and water, shelter, competition

6. V. Competition
Competition is when organisms attempt to use the same limited ecological resource in the same place, at the same time
Ex: Plant competition – invasive species
Ex: Animal competition –

7. V. Competition
D. Competition between the same species is known as intraspecific competition
E. Competition between differing species is known as interspecific competition
F. There is ALMOST always a winner and a loser (likely the loser will die)
G. Ex: 2 species of bacteria growing in different dishes – both live. Grown in the same dish – will compete and one will die off

8. VI. Competitive Exclusion Principle
A. The Competitive Exclusion Principle
- No 2 species can occupy exactly the same niche in exactly the same habitat at exactly the same time

9. VI. Competitive Exclusion Principle (Example)
B. Some species divide resources instead of competing (Yes! Animals share, sometimes)
C. Ex: Warbler birds – live in SAME tree with other warbler birds, and all eat insects
D. One species feeds on higher branches, another in the middle, another on lower branches
E. Each occupies its OWN, separate niche

10. F. Each species has its own niche and doesn’t compete for food as long as it doesn’t leave its niche
G. What would happen if 2 species occupied the same niche in the same tree at the same time?

11. VII. Relationships in Communities
There are MANY types of relationships between members in a community
Need to know def. and examples of each:
Predation
Herbivory
Keystone species
D. Mutualism
E. Parasitism
F. Commensalism

12. VII – A. Predation
Predation – interaction when one animal captures and feeds on another animal
Predator – prey relationship
Predators can affect the size of prey populations in a community and determine the places prey can live in and feed
Ex: Think of the predators from Planet Earth videos – is this true?

13. VII. – B. Herbivory
Herbivory – interaction when an animal (herbivore) feeds on a producer (plant)
Herbivores can affect both the size and distribution of plant populations in a community
Can determine the places that certain plants can survive and grow

14. VII. – C. Keystone Species
Keystone species – single species that is not usually abundant in a community, yet exerts strong control on the community’s structure
Ex p.103: Sea otters of Pacific coast feed on lots of sea urchins; urchins are herbivores that eat kelp (giant algae)
What happens if otters are wiped out?

15. VII. *Symbiotic relationships
* Symbiosis – any relationship in which two species live closely together
* Mutualism, parasitism, and commensalism are symbiotic relationships, meaning the organisms involved have a LITERALLY close relationship (live in each other’s space)

16. VII. – D. Mutualism
Mutualism – relationship in which both species benefit
Ex: Finding Nemo: sea anemone and clownfish – clownfish hide from predators in deadly tentacles (have a special coating so they don’t get stung); anemone get cleaned and protected by territorial clownfish – some will even bring food to it

17. VII. – D. Mutualism
3. Ex: Stomach bacteria – breaks down carbohydrates for the human, but also feeds on some
4. Ex: Flowers and pollinators –
pollinators (bees, butterflies) get food; flowers get their pollen transferred

18. VII. – E. Parasitism
Parasitism – relationship in which one species benefits and one species is harmed
Parasites typically live in or on a host
Ex: Tapeworms live in intestines, feed on host’s blood, taking nutrients from host
Ex: Ticks, fleas, lice, leeches – live on host and feed on blood – often transmit disease

19. VII. – F. Commensalism
Commensalism – relationship in which one organism benefits, and the other is neither helped or harmed (is unaffected)
Ex: Barnacles attached to whale’s skin – don’t harm the whale or provide any service, yet barnacles benefit
by constant movement thru water allows them to filter feed much more easily

20. Battle at Kruger Overall theme – Competition
See if you can find other concepts being played out
Niche, physical or biological factors, resources, habitat, tolerance, types of competition
You will write a paragraph (5 – 7 sent) reflecting on what you learned