Biology 20- Unit B: Ecosystems + Population Change: Topic 2

Mechanisms of Population Change

Adaptations

Changes in physical structure, function, or behavior that allow an organism or species to survive and reproduce in a given environment.

Structural Adaptations

Physical features that improve one's chances for survival
Ex. Camouflage; when an animal blends in with its environment

Behavioral Adaptations

The way an organism acts that makes it better suited to its environment
Ex. Squirrels bury nuts during the summer and fall so they'll have enough food for the winter

What are physiological adaptations?

A metabolic or physiologic adjustment within the cell or tissues of an organism.

What triggers physiological adaptations?

An environmental stimulus.

What is the result of physiological adaptations?

Improved ability of the organism to cope with its changing environment.

Give an example of a physiological adaptation.

Formation of callouses on hands in response to repeated contact or pressure.

What is the source of adaptations?

The gradual change in the characteristics of a population over time

Phenotype

An organism's physical appearance, or visible traits.

Genotype

An organism's genetic makeup, or the specific allele combinations.

Variation

Result of genetic changes and recombinations

Alleles

The different ways a gene can code for the same part of an organism
Ex. Eye colour

Mutations

A random error in gene replication that leads to a change

Mutagenic Agents

chemical or physical agents that can cause mutation in DNA

Somatic Cells

Makes up body tissues

If mutations are present in somatic cells:

These mutations will disappear when the organism dies

Germ Line Cells

cells that produce eggs and/or sperm

If mutations are present in germ line cells:

the mutations will be passed on to the next generation

Selective Advantage

a genetic or phenotypic characteristic that enables an organism to survive and reproduce better than others in a given environment

Natural Selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

Selective Pressure

when the environment pushes an individual or population to adapt or evolve

For natural selection to occur, there must…

be variation within the species

Variation within species

refers to the genetic, physical, or behavioral differences among individuals of the same species

What happens if a variation is detrimental?

It becomes unlikely that the variation will be passed on until the environment changes to select for that variation

Intraspecific Variation

Variations occur within each species

Interspecific Variation

Variations occur between species which creates new species

Speciation

the evolutionary process by which new, distinct species arise from existing ones, occurring when populations become reproductively isolated and diverge genetically

Transformation

Accumulated changes in a population over time
Result of natural selection

Divergence

One or more species arise from a parent species that continues to exist; greater biodiversity
Result of natural selection

Geographical Barriers

keep populations physically separated

What must be prevented for speciation to occur?

Interbreeding of populations

Reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

Biological Barriers

Behavior (courtship of bird songs)
Pheromones (chemical signals)
Different habitats

Adaptive Radiation

the diversification of a common ancestral species into a variety of differently adapted species

behavioral isolation

Form of reproductive isolation in which two populations have differences in courtship rituals or other types of behavior that prevent them from interbreeding

Geographic isolation

form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water

Survival of the Fittest

organisms best adapted to their environment are the most likely to survive and reproduce

Fossil Record

Chronological collection of life's remains in sedimentary rock layers
Ex. Burgess Shale

Transitional Fossils

Fossils that provide patterns of evolutionary change from the early ancestors to modern life forms.

Radiometric Dating

method used to determine the age of rocks using the rate of decay of radioactive isotopes

Biogeography

Study of past and present distribution of organisms

Endemic

native or confined to a particular region (species that are found nowhere else)

homologous features

structures that have a similar build regardless of function
Ex. limbs of a human, cat, bird

Analogous features

similar in appearance and function, but do not have the same evolutionary orgin

Artificial Selection

Breeding individuals with desired characteristics in order to get offspring with those same characteristics

Embryology

study of embryos and their development

Gradualism

Gradual change occurs steadily in a linear matter

punctuated equilibrium

long periods of evolutionary equilibrium are interupted by periods of speculation

Evolutionary equilibrium

a state of stability in a species' evolution, characterized by long periods of little to no morphological change, often interrupted by rapid bursts of speciation