1. Populations C-5-1

2. Exponential Growth
Populations can grow exponentially if not kept in check.
~ for instance: one bacteria will become 2, then 4 then 8,then 64, then 512,then at the end of one day, there will be 4.72 x1021

3. Exponential Growth
only happens when populations have every offspring survive to reproduce.
As resources become less available, offspring don't live as well. This stops population growth.
Carrying capacity
max # org. an ecosystem can support

4. Exponential Growth
Human population has grown exponentially since the 1700's.
due to medicine and farming technology:
people live longer lives
vaccines lower death rates
more food supports more people
We have not reached carrying capacity yet, but some evidence shows we may reach 9 bill. by 2060

5. Ecosystems are influenced by a combination of biotic (living organisms) and abiotic (physical) factors.

6. Limiting Factors for populations
Density-dependent
Competition for food - more org. = less resources
Predation - predator-prey relationships keep each other in balance
Parasitism and Disease - keeps populations down by killing host

7. Limiting Factors for populations
Density-indepenant
Drought / Climate extremes – extreme heat or cold, lack of or too much water...all can kill
Human disturbances - changing the ecosystem ~ deforestation, waste dumping, killing off predators

8. DDF - only become limiting when the pop
DDF - only become limiting when the pop. density reaches a certain level
DIF - affect all pops. similarly regardless of pop. size
Through a combination of all of these factors, populations can vary from being in balance, to being way out of balance.

9. Interaction in Communities C-5-2

10. There are many different ways species can interact with each other within their communities...

11. Interactions Competition Predation
species have similar needs and compete for survival
Predation
one org. eats another
back and forth adjustment between the 2 results in coevolution
ex: the faster the prey gets, the faster the predator gets and vice versa

12. Interactions
Symbiosis - relationship where 2 species live closely together.
3 types:
a.) Mutualism - both species benefit
ex: flowers and insects
b.) Commensalism - one benefits, the other is neither helped or harmed
ex: barnacles on a whale
c.) Parasitism - one org. lives on another and the host is harmed
ex: tapeworms in mammals

13. Shaping Communities C-5-3

14. Habitat
area in which an org. lives

15. Niche - all conditions in which an org
Niche - all conditions in which an org. lives and how it uses those conditions
type of food eaten
place in the food web
temp. in which they survive
reproduction style
Fundamental niche - where a species could live
Realized niche - where a species actually lives

16. No two species will share the same niche in the same habitat!

17. Competitive exclusion principle
no 2 species can occupy the same niche in the same habitat at the same time
this would result in the elimination of one of the species

18. keystone species
these are critical to the ecosystem because they affect the survival and number of many other species in their community
Ex. Sea otters

19. Ex: sea otters: sea urchins eat kelp - sea otters eat sea urchins
when sea otters are over hunted, too much kelp gets eaten by urchins - all other species that use the kelp to live in lose their home.
sea otters are critical to the survival of the ecosystem

20. Summary The more species in a community, the better
It will recover from disasters.
The predators help insure that no one species takes over.
More biodiversity = better resiliency