Limits to growthLecture 5-2

Limiting factors

W/B: what is the limiting nutrient?

Many factors can limit population growth.

They can be either density- dependent

or density-independent

A limited resource base can also affect the long-term survival of a species.Ex: Pandas and habitat loss

ChinaHabitat loss has reduced the bamboo forests the Pandas eat.

Density-dependent factors

P/S: what will the puffins compete for?

Become important when population density is high- the # of individuals per a certain area.

#1Competition: for food, water, sunlight, space can happen within a species and between species

#2: Predation

W/B: what year had the most wolves? What year had the most moose?

Increases in the prey population are followed by increases in the predator population.

If the predator dies, the prey numbers will rise again.

#3. Parasitism and disease

Parasitized moth larvae(hornworm)

The parasitic wasp lays its eggs on the moth larvae. The wasp larvae feed on their host as they grow.

Parasites act similar to predators, taking nourishment at the expense their hosts.

They weaken the host, causing disease or death

Sphinx moth

Parasitic wasp

Density-independent factors

P/S: what tolerance levels were exceeded for these species?

Affect all populations in an area in similar ways.

#1 Extreme weather

Storms, drought, extreme cold can cause many populations to crash

#2 Human activity

3 gorges dam, China2000 and 2006 (satellite image)

AgricultureDamming riversCutting forestsCities and streetsPollution Humans have caused

rapid changes to ecosystems, adversely affecting many species.

W/B: what % of the land in this picture is ‘natural’?

Today’s talk was about……. I already knew about……….. I just learned that……… I wonder why…………

summary