ecology and evolution. evolution define: – the change in a populations genetic composition over...
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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