Ecology and Evolution

Evolution

• Define:– The change in a populations genetic composition over

time

• Models of Evolution:– Phylogenetic Tree: shows how organisms are

evolutionarily related

• Process by which evolution causes the emergence of new species:– Speciation

Species

• Define:– A group of organisms that are capable of interbreeding

with one another, and incapable of breeding with other species

• Evolutionary Fitness:– Described by Darwin– When individual organisms are better adapted to their

environment they will live and reproduce longer. If they live longer and reproduce more the individuals will pass on their genes to the next generation of the population

How Evolution Works

• Natural Selection acts on a population:– The organisms environment exerts pressures on

them which causes certain organisms to live and others to die

– If an individual lives and reproduces, they have genes which allow them to survive in their habitat better

– If an individual dies, they had inadequate genetics to allow them to survive

Gene Pools

• The consequence of natural selection is that total genetic make-up of the population changes

• Gene Pool:– The total conglomeration

of all the different genes of a population

Time Scale

• Macroevolution– Large scale changes

over a long period of time

• Microevolution– Small scale changes

over a short period of time

Extinction

• Define:– When a species of

animals completely dies out

• Why do species die out?– Populations of species

cannot adapt fast enough to the changing environmental conditions

Basic Vocab• Niche:

– The total sum of a species use of biotic and abiotic resources in the environment

• Community:– A population of different species living in a specific geographic area

• Habitat:– An area of an environment where an organism or ecological

community normally lives

• Population:– A group of organisms of the same species occupying a specific area

Niche

• Describes:– Where species live– What species eat– How a species utilizes resources in an ecosystem

• Is an organisms particular ‘role’ in an ecosystem

• When niches overlap….– You get competition

Competition

• Define:– When there are two individuals fighting for particular

resources– Can occur between different species or within species

• Intraspecific Competition:– When there is competition between members of the same

species

• Interspecific Competition:– When there is competition between members of different

species

Competition cont.….

• Resources that can be competed for:– Air, light, food, shelter, land, water, and even

places to reproduce…in other words EVERYTHING!

• The individual who is ‘most fit’ or can exploit the resource best will survive– The other will be eliminated

Exclusion

• Competitive Exclusion– Occurs when two different species compete in a

region and the best adapted species wins and survives

• Gause’s Principle:– States that no two species can occupy the same

niche at the same time– One will occupy the niche, the other will die out,

relocate, or occupy a different niche

Fundamental vs. Realized

• Fundamental Niche:– The most ideal niche for an organism if

competitive exclusion is not present

• Realized Niche:– The niche a species occupies after it has been

competitively excluded

Relationships

• Predation:– When one species feeds on another, and is a major

population size control• Symbiotic– Prolonged association between individuals of 2 or

more species– 3 different types of symbiotic relationships

• Mutualism – both individuals benefit• Commensalism – one benefits but the other does not• Parasitism – one benefits but the other is harmed

Relationships: Examples

Ecology

Keystones

• A keystone species is:– A species one that maintains the biotic balance in

community– Important because biodiversity is a direct

consequence of the presence of this organism– Ex: Wolves in Yellowstone

Indicators

• An indicator species is:– A species that is used to evaluate the health of an

ecosystem– Are typically more sensitive to environmental

changes than other species– Act as an ‘early warning system’

Natives

• Indigenous species:– Is a species that is native to a particular habitat,

environment, or region– Are naturally occurring in areas– Ex: Grey Squirrel in Wisconsin

Invaders

• Invasive Species:– Is a species that is not native to a region or area– Will typically disrupt the ecology of the area and

cause massive problems– Ex: Buckthorn in Waukesha and Wisconsin, Asian

Carp in Lake Michigan, Zebra Mussels in Lake Michigan, Chestnut Blight in the U.S., Emerald Ash Borer in the U.S.

Succession

Bare Rock ------- > Forest

• Ecological Succession– The flow of biological development in an area after a

disturbance– Disturbance = fire, lava forming, flooding, others…

• Primary Succession:– When ecological succession occurs in an area that has been

disturbed so bad that there is nothing living (Ex: glacier, lava)

• Secondary Succession:– When ecological succession occurs in areas where the

community has been cleared but left somewhat intact– Ex: fires, floods, tornadoes, or human impacts

Pioneers to Community

• Pioneers Species:– Is a species that is the first to arrive at a disturbed area– Typically have a wide range of environmental tolerances– Drive the environmental changes that allows the next

stage of succession to occur

• The climax community:– The final stage of succession– When there is a dynamic balance between abiotic and

biotic components of the community– Very little change in the community

How Succession Occurs

• Step 1: Bare Rock• Step 2: Lichen, algae, moss, and bacteria

colonize the rock and begin to break down the rock and leave behind organic debris

• Step 3: Grasses grow, add more organic material to the soil, and hold the new soil in place

• Step 4: Small herbaceous plants add further organic debris to the soil

How Succession Occurs

• Step 5: Small bushes grow, add microhabitats, add shade and shelter from the sun, and add organic debris to the soil

• Step 6: Conifers sprout and grow thus adding further microhabitats to the area

• Step 7: Short-lived hardwoods grow which include dogwood and red maple. Shade tolerant trees.

• Step 8: Long-lived hardwoods grow that are specialized and hardy. Includes oak trees and hickory trees