speciation

Speciation definition

Splitting of 1 species into 2 or more species

Types of natural selection

• disruptive selection

• Directional selection

• Stabilizing selection

Disruptive selection

Both extremes of a trait are favoured

Directional selection

One extreme is favoured

Stabilizing selection

Intermediate or middle trait is favoured

What is the Hardy-Weinberg equilibrium?

It is a state where evolution isn’t occurring, so allele frequencies are staying the same

Unrealistic situation

What are the Five conditions that must be met for Hardy Weinberg equilibrium to occur

• no natural selection

• No mutation

• No migration

• Large population

• Mating is random

allopatric definition

species that is geographically separated

sympatric

Species living in the same geographic area

groups diverge because of different behaviour, food source, or genetics

Allele frequency equation

p + q = 1

Genotype frequency equation

p^2+2pq+q^2=1

Cladistics purpose

Way to determine evolutionary relationships between species based on shared traits and genetic evidence

What is a clade?

Made up of all species that have evolved from a single common ancestor

Behavioural isolation

Pre-zygotic

Different species use different courtship and other mating clues to find an attract a mate

Temporal isolation

Pre-zygotic

Different species breed at different times of the year

Ecological isolation

Pre-zygotic

Very similar species may occupy different habitats within a region

Mechanical isolation

Pre-zygotic

Difference in morphological features may make two species incompatible

Gametic isolation

Pre-zygotic

Male gametes may not be able to recognize and fertilize an egg of a different species

zygotic mortality

Pro zygotic

Mating and fertilization is possible, but genetic differences result in zygote that’s unable to develop properly

Hybrid inviability

Prozygotic

Hybrid individual develops but dies before birth or born alive, but can’t survive to maturity

Hybrid infertility

Hybrid offspring remain healthy and viable, but are sterile

What is a cladogram?

Tree diagram showing the similarities and differences between different species

What are cladograms based on?

Mostly based on DNA base sequences or amino acid sequences in a protein

Theory of evolution

• all life is related

• All life has descended from common ancestry

• Complex organisms descend from more simplistic organisms over time

• Random, genetic mutations result in benefits that aid survival and her past to future generations, also called natural selection

evidence for evolution

• fossils

• Embryology

• Similar DNA sequences indicate common ancestry

• Homologous structures