Populations C-5-1

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

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

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

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

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

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

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.

Interaction in Communities C-5-2

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

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

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

Shaping Communities C-5-3

Habitat area in which an org. lives

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

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

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

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

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

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