Week 3

genes

short segment of a chromosome that encodes for a specific protein

Alleles

different types of the same gene

Homozygous

the alleles are identical

Heterozygous

the alleles are different

Dominant

a trait that will mask the expression of any other allele

Recessive

masked by a dominant allele, invisible will only express itself in the homozygous

Simple Patterns

alleles obey the law of segregation and independent assortment, inheritance patterns of traits affected by a single gene that is found in 2 variants

Pisum sativum

common garden pea that Mendel studied it had many varieties differing in characteristics

True Breeding Line

organisms with a given phenotype that produce offspring with the same phenotype generation after generation

Phenotype

the physical appearance of an organism controlled by the genotype

Genotype

An organism's genetic makeup, or allele combinations.

Cross - Fertilization

removal of pollen from plant and selectively pollinating the female reproductive structures of different plants

Monohybrids

offspring of true breeding parents that differ in only one character

Mendels Law of Segregation

Mendel always observed a 3;1 ratio between dominant and recessive traits in the F2 generation

which chromosome has more information on it

X chromosome

Males

XY

Females

XX

Y chromosome

gene for testis determining factor (TDF)

Sex Linked Traits

coded for by genes located on the sex chromosomes, mostly X

Incomplete Dominance

both alleles are partially expressed in the heterozygote

Codominance

if 2 dominant alleles for a given trait are inherited both will be fully expressed

Epistasis

a type of gene interaction in which the alleles of one gene masks the effects of an allele of another gene

Continuous Variation

inheritance pattern in which offspring display a continuous range of phenotypes

Autosomal Linkage

all the genes that are located on the same chromosome are said to be linked may be broken up during meiosis

X chromosome Inactivation

in female mammals, one X sex chromosome is inactivated in the somatic cell, RANDOM

Evolution

change in gene frequencies in a population over time

Carolous Linnaeus

father of modern taxonomy, classified organisms based on their similarities

LaMarck

first to propose a mechanism for evolution (inheritance of acquired characteristics)

Inheritance of acquired characteristics

if your dad cuts your pinky off you won't be born without a pinky

Charles Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

HMS Beagle

charted coastlines in the Southern Hemisphere and brought Darwin to the Galapagos Islands

Darwins Theory of Evolution

Those individuals that are best adapted to the environment will survive and reproduce; those traits that help them, become more common in a species and maladaptive traits die out. This is called natural Selection.

Fossil Records

some fossils show a change in a species overtime EX horses hoof

Convergent Evolution

unrelated species that evolve similar characteristics under similar circumstances

Selective Breeding

animals can only breed with other animals of the same species

Vestigial structures

organs which appear to not be used by one species but are highly developed in another

Macroevolution

evolutionary changes creating new species and groups of species, accumulation of microevolutionary changes

Morphological Traits

physical characteristics, disadvantage is you don't know how dissimilar traits are

Reproductive Isolation

inability to breed in nature, disadvantage is sometimes different species can interbreed in nature

Molecular Features

comparisons of DNA sequences of genes and location of genes, disadvantage is you don't know how different the features need to be

Ecological Factors

related to an organisms habitat, EX some warbler species characterized by where they forage for food

Evolutionary Relationships

MOST ACCURATE, based on fossil record and DNA analysis

Species Concepts

a way to define concept of a species and/or provide approach to distinguish different species

Biological Species Concept

group of individuals capable of interbreeding with one another in nature to produce viable, fertile offspring, can't interbreed with members of other species

Evolutionary Lineage Concept

species defined based the separate evolution of lineages

Ecological Species Concept

each species occupies an ecological niche (unique set of habitat resources)

General Lineage Concept

each species forms a group with a particular set of characteristics, DNA sequences can be applied to all organisms

Reproductive isolating mechanisms

mechanisms that prevent interbreeding between different species

Prezygotic Isolating mechanism

prevents a zygote from forming

Zygote

a single cell formed when an egg is fertilized by a sperm

Habitat Isolation

species can't breed because they occupy different habitats, never come in contact with each other

Temporal isolation

reproduce at different times of the year

Behavioral Isolation

differences in behavior or physiology prevent attraction between males and females even if they live in the same habitat

Mechanical isolation

body parts don't fit together to exchange gametes

Gametic isolation

games fail to unite successfully,
protein called binding allows sperm to attach to the ova but this doesn't happen in gametic isolation

Postzygotic isolating mechanisms

reduced viability or reproductive capacity of hybrid offspring, less common in nature

Hybrid inviability

egg of one species is fertilized by a sperm from a different species, development of zygote stops during early embryonic stage

Hybrid sterility

a viable hybrid is produced but sterile EX mule

Hybrid Breakdown

interspecies hybrids are produced and are fertile but subsequent generations harbor detrimental genetic abnormalities

Speciation

Formation of new species which happens because the environments affects the phenotype which affects the genotype

Anagenesis

SINGLE species transformed into different specieS over the course of many generations

Cladogenesis

division of a species into 2 or more species (original may still be alive)

Allopatric Speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.

Genetic Drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

Adaptive radiation

one species evolves into many descendent species differing greatly in habitat, form or behavior

Sympatric Speciation

The formation of a new species as a result of a genetic change that produces a reproductive barrier between the changed population (mutants) and the parent population. No geographic barrier is present.

Timespan of Speciation

rate of evolutionary change and speciation not constant

Gradualism

new species evolve continuously over long spans of time

Punctuated Equilibrium

long periods of evolutionary stasis are interrupted by short rapid bursts of changes in phenotypic frequencies (rapid evolutionary change)