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