Patterns of Evolution:

Divergent Evolution:

Ancestral species evolve into 2 or more species
- Become specialised to occupy different niches
Involves formation of a large number of species from ancestral species
- Due to the availability of many niches
Associated with Homologous Structures
- Different functions
- Same ancestral origins
- Evolve differently

Convergent Evolution:

2 or more unrelated species evolve to resemble each other
Develop similar features in response to similar niche requirements
Associated with Analogous Structures
- Different ancestral origins
- Similar functions
- Similar appearances
- Evolve similarly

Adaptive Radiation:

Different groups able to occupy a wide variety of different ecological niches recently become available
A form of divergent evolution
- The rapid evolution of a number of different species from the same ancestral origin

Co-Evolution:

2 different species ecologically intimate
- Influence each other’s evolution
Evolutionary changes in one species
- That species acts as a selection pressure on another
- Vice Versa
Has 3 forms
- Predator-Prey
  - Predator and prey evolve together
  - Predator evolves whatever necessary to eat prey
  - Speed, camouflage, heightened sense, immunity to prey’s poison, own poison
  - Prey evolves whatever necessary to avoid the predator
  - Speed, camouflage, heightened senses, own poison, thorns
- Mutualistic
  - A relationship develops because of selection pressures
  - Develop adaptations for the benefit of each other’s niche requirements - gain survival advantages
  - Mutual benefits for both species
  - Greater reproductive success
  - Pass on their favoured alleles
- Parasitic
  - Parasite causes harm
  - Takes nutrition from the host
  - Lifecycles in or on the host
  - Lives outside the host (external parasites)
  - Lives inside the host (internal parasites)

Phyletic Gradualism:

Evolutionary model that occurs as a slow steady process
Organisms change and develop slowly over time
Small periodic changes in the gene pool
Natural selection gradually changes the average features of species
- Removes less fit individuals
- Increases fit individuals
Not concentrated in lineage-splitting evolution
- Have non-straight lines in morphology graph
- Single species gradually change into new species - original goes extinct

Punctuated Equilibrium:

Evolutionary pattern
- Connected to speciation events
- E.g RIM's
Species undergoing very little evolution for long periods of time
- Before suddenly evolving rapidly
Statis (straight line)
- Lack of substantial change over millions of years
Happens to small populations that have become isolated from original species

Causes of Punctuated Equilibrium:

Mutations - Punctuated Equilibrium:

Change in environment - Punctuated Equilibrium:

Stage 1: statis
- Organism living, dying
Stage 2: isolation
- A sudden change in environment e.g drop in sea level forms lake
- A small number of population of organism isolated
Stage 3: selection pressures
- Small population experiences strong selection and rapid change
- New environment formed - new selection pressures
Stage 4: no preservation

	Created by Shivani Kershaw almost 6 years ago

Not full notes for external - brief notes for a TOPIC TEST.