Understanding Populations

1. Understanding Populations Ch8, Section 2: How Species Interact with Each Other Standards: SEV3e, SEV5a, b

2. What is a specie’s niche? • Niche- role a species has within an ecosystem. • Includes: • Species physical home • Factors needed for survival • Interactions with other organisms • Ex: Bison are grazers & help control tree sapling populations as well as fertilize soil for grass • Ex: Fungi & bacteria are decomposers, recycling nutrients to soil.

3. What is a specie’s habitat? • Place where a species lives • An organism performs its niche in its habitat.

4. How do species interact with each other? • Competition • Predation • Parasitism • Mutualism • Commensalism

5. 1. Competition • Relationship where individuals or populations share limited resources • Both species are harmed • -/- interaction • Intraspecific competition- within the same species. • Ex: caterpillars of the same species eating the same leaf. • Interspecific competition- between different species • When members of different species compete we say their niches have overlapped. • Ex: hyenas compete for kill with lions

6. 1. Competition • Indirect competition- compete even though they do not come in contact with each other. • Ex: An insect that eats a leaf during the day competes indirectly with an insect that eats the same leaf at night. • Ex: Plants compete for pollinators; humans compete with insects for food crop.

7. 1. Competition • Adaptations to competition- • When 2 species compete for a resource, usually only one will win. • The other species must move to find new resources. • This is called competitive exclusion.

8. 1. Competition • Competitive exclusion can lead to niche restriction. • These species share the same niche & habitat but use a smaller portion of it. • Ex: Two barnacle species Chthamalus & Balanus • share the same intertidal zone of a rocky shore line • Chthamalus lives at higher tide line (realized niche) • When Balanus is removed, Chthamalus will move further down into the original Balanus habitat. (fundamental niche) Realized niche- where the species actually lives Fundamental niche- where the species could live if given a chance.

9. 2. Predation • Predator feeds on prey • Predator benefits, prey is harmed • +/- interaction • Some predators are very specific about what they eat • Canadian lynx only eat snowshoe hares • Creates predator/prey oscillations • Most predators generally eat any prey they can capture • Not all predators are carnivores

10. 2. Predation • Animals adapted to avoid predation: • Camouflage- hard to see; blend in • Ex: some caterpillars; lizards • Warning coloration- alert potential predator that they are dangerous • Ex: poison dart frogs • Mimicry- look like something more dangerous even if it isn’t • Ex: some flies have same coloration as bees • Protective coverings- too hard for predator to eat. • Ex: porcupine, turtle, cactus

11. 3. Parasitism • Parasite lives and feeds on host organism. • Parasite benefits, host is harmed • +/- interaction • Parasites are different from predators because they do not usually kill their host (what else would they eat if they killed their host?) • Parasite can weaken host & make them more susceptible to disease. • Ex: ticks, leeches, mistletoe, fleas

12. 4. Mutualism • Each species benefits from the relationship • +/+ interaction • Some species couldn’t live without each other • Ex: bacteria in your intestine; acacia tree & ants; insects & flowers

13. 5. Commensalism • One species is benefited and the other is neither harmed nor helped. • +/0 interaction • Ex: orchids in trees; clownfish & anemones; remoras and sharks

14. What is Symbiosis • Relationship where two species live in close association • Often one species benefits. • Which of the five species interactions are considered symbiosis?

15. What is Coevolution? • When species have such close relationships they often coevolve. • These two species would be less likely to survive if one were missing. • Ex: bee orchids