1. Limits to growth Lecture 5-2

2. Limiting factors • Many factors can limit population growth. • They can be either density- dependent • or density-independent W/B: what is the limiting nutrient?

3. A limited resource base can also affect the long-term survival of a species.Ex: Pandas and habitat loss China Habitat loss has reduced the bamboo forests the Pandas eat.

4. Density-dependent factors • 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 P/S: what will the puffins compete for?

5. #2: Predation • Increases in the prey population are followed by increases in the predator population. • If the predator dies, the prey numbers will rise again. W/B: what year had the most wolves? What year had the most moose?

6. #3. Parasitism and disease • Parasites act similar to predators, taking nourishment at the expense their hosts. • They weaken the host, causing disease or death Parasitic wasp Sphinx moth Parasitized moth larvae (hornworm) The parasitic wasp lays its eggs on the moth larvae. The wasp larvae feed on their host as they grow.

7. Density-independent factors • Affect all populations in an area in similar ways. • #1 Extreme weather Storms, drought, extreme cold can cause many populations to crash P/S: what tolerance levels were exceeded for these species?

8. #2 Human activity Agriculture Damming rivers Cutting forests Cities and streets Pollution • Humans have caused rapid changes to ecosystems, adversely affecting many species. 3 gorges dam, China 2000 and 2006 (satellite image) W/B: what % of the land in this picture is ‘natural’?

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