1. Niches and Community Interactions
Unit 5 Section 2

2. Why do organisms live where they do?
Each species has a range of conditions under which it can grow and reproduce
These conditions help define where and how an organism lives

3. Habitat and Niche Habitat – place where an organism lives
Example: Habitat of a bullfrog is a pond
Think of it like an organism’s address
Niche – Occupation of an organism
Includes: how it gets its food, reproduces, avoids predators, etc.
Niche determines its habitat
Example: woodpeckers can’t live in grasslands because their niche is to find insects in tree trunks!!

4. Competition
Organisms often try to use a limited resource in the same place at the same time as other organisms
This is called Competition
Can occur between the same species or different species
Compete for things like: food, space and mates
Competition results in natural selection. Only those with the best traits for that environment will survive and reproduce
No two species can have the same niche in the same environment at the same time this is called the competitive exclusion principle

5. Predator-Prey Relationships
Predation:
Members of one population are the food source for members of another population
Predator – organism doing the eating
Prey – organism that is being eaten
Predator keeps the prey population from getting too big

6. Herbivore-Plant Relationships
Herbivory – when herbivore feeds on a producer
Keeps the plant population from getting too large

7. Keystone Species
A population change in one species can cause dramatic changes in a community
This is called a keystone species

8. Symbioses
Symbiosis – any relationship in which two species live closely together
Three main types of symbiotic relationships
Mutualism
Parasitism
Commensalism

9. Mutualism Mutualism – both organisms benefit
Clownfish is immune to sea anemone stings and gets protected from predators
Sea anemone gets protection from clownfish who chases away bigger fish that try to eat it

10. Parasitism
Parasite – lives on or in another organism that it uses for food and sometimes for shelter
Host – organism the parasite uses
One organism is helped while the other is harmed
Host organism continues to live and is not killed right away just harmed
Examples: tapeworms, flukes, ticks

12. Commensalism
One organism benefits and the other is neither helped nor harmed
Barnacles attach themselves to whales and benefit from constant movement of water and food particles past the swimming whale
Whale is neither harmed nor helped by the barnacle