Do Now, 4.17 (HW check)OBJECTIVES:

1.Complete yesterday’s objectives

2.Describe interspecific interactions, including: predation, herbivores, competition, symbiosis,

parasitism, mutualism, commensalism, and mimicry.

3.Define and distinguish habitat and niche

TASK:

Complete the front of the “Population Practice Problems” worksheet from yesterday

Population Interactions

Predators and their Prey• Predator survival depends on capturing

food.

• Prey survival depends on hiding, escape, or other defenses.

• Since only successful organisms survive and reproduce, the genetic material of the best (or luckiest) organisms gets passed onto the next generation. This is called natural selection.

Plants and Herbivores• Animals that eat plants = herbivores.

Some plants produce poisonous or bad-tasting secondary compounds as a defense against herbivores… but not the grass this cow is munching!

Competition

• Resources (like food / energy) are limited. When two populations share the same niche, they will compete for use of that resource.

• Do human populations compete for resources?

• What resources?

Competitive Exclusion: One species is removed from the community because it could not get enough of the resource

Resource Partitioning: Several species use part of the available resource, reducing competition.

Symbiosis

• Symbiosis is the close association between two or more different species or organisms.

• Three main types– Parasitism– Mutualism– Commensalism

Parasites and Parasitism• A parasite feeds on its host.• Similar to predator / prey, but the prey isn’t

usually killed.• Endoparasites are internal, Ectoparasites

aren’t.

Endoparasite: Trichonella

Ectoparasite: Deer tick

Mutualism

• A cooperative relationship where both organisms benefit

CommensalismOne organism benefits, the other is unaffected

Mimicry

• A harmless organism resembles a poisonous or distasteful one.

Or…

More Mimicry• Several poisonous or distasteful species

look similar

Habitat: the particular place in which an organism lives.

Niche: the unique role an organism plays in its environment.

Habitat: Humans & Polar Bears

Polar bears can be found on pack ice, coastal islands, coastlines and even out in Arctic waters. They are exceptional swimmers and have been observed in the sea more than 100 miles from

the nearest land or pack ice.

A majority of human beings live in urban environments

Urban Land:

3% of Earth’s land surface

3,500,000,000 people

Niche: Humans & Polar Bears

Polar bears are strictly carnivores and feed or scavenge only meat. Their primary prey is the ringed seal though they also take bearded, harp and hooded seals and the occasional walrus youngster. They will also scavenge walrus and whale carcasses.

Humans generally eat plants and animals grown using technology such as chemical fertilizers and irrigation.