Genetics and Evolution Overview

Discontinuous Variation

Indiviudal shows one of two or easily distinguishable traits (blood type)

Fossils

Remains of organisms from past geological periods

Artificial Selection

Selective breeding by humans for desired traits

Stabilizing Selection

Selection against extreme phenotypes

Biological Species Concept

Defines a species as individuals capable of interbreeding

Honeycreepers on Hawai'i

Example of adaptive radiation in bird species

Genetics

Study of genes and heredity

Gene

carried chromosomes are the basic functional units

Locus

Specific position on a chromosome

Genotype

underlying genetic make-up

Heterozygote

Individual with two different alleles for a gene

Homozygote

Individual with two identical alleles for a gene

Continuous Variation

Range of phenotypes with no distinct categories

Punnett Square

Tool to predict offspring genotypes

Law of Dominance

Mendel's principle of one allele masking another

Law of Independent Assortment

Mendel's principle of genes segregating independently

Polygenic Trait

Trait influenced by multiple genes

Epistatic Genes

Genes that mask the expression of other genes

Pedigree

Family tree showing inheritance of traits

Divergent Evolution

Species evolving in different directions from a common point

Vestigial Structures

Remnants of structures with no apparent function

Gene Pool

All genes in a population

Genetic Drift

Random changes in allele frequencies

Founder Effect

New population established by a small group

Non-Random Mating

Mating based on preference, not chance

Mutation

Change in DNA sequence

Peppered moths

Example of natural selection due to industrial melanism

Apple fly maggot

Example of sympatric speciation in the same habitat

Allele

Alternative form of a gene

Phenotype

Observable traits of an organism

Mendel

Father of genetics, studied pea plants

Evolution

Change in allele frequencies over time

Natural Selection

Process where favorable traits increase in a population

Convergent Evolution

Similar structures evolving independently

Population

Group of individuals of the same species in a given area

Bottleneck Effect

Population reduction leading to loss of genetic diversity

Gene Flow

Movement of alleles between populations

Directional Selection

Shift towards a specific phenotype

Diversifying Selection

Selection for extreme phenotypes

Diversifying/Disruptive selection

Selects for extreme phenotypes, against intermediate ones

Bill size in hummingbirds

Example of adaptive radiation and niche differentiation

Reproductive isolation

Prevents interbreeding between species through barriers

Speciation

Formation of new, distinct species through evolution

Geographic isolation

Type of speciation where physical barriers separate populations

Vicariance

Geographic isolation by physical barriers like mountains or rivers

Prezygotic Barriers

Mechanisms preventing mating or fertilization

Postzygotic Barriers

Mechanisms reducing hybrid viability or fertility

Adaptive Radiation

Rapid diversification of a single species into many