4.3 Formation of a new species

variation in population examples

• Different beak forms of Galapagos finches

• anti-biotics resistant bacteria

Inbreeding definition

mating of genetically closely related individuals

Inbreeding consequences

• loss of genetic diversity, prevents evolution

• results in homozygosity which can increase the chances of offspring having recessive/harmful traits

Inbreeding depression

• lower birth weight

• less resistance to disease, predators and environment

• less successful reproduction

Outbreeding definition

production of offspring from the mating or breeding of genetically unrelated individuals

outbreeding outcomes

• increases genetic variation

• promotes heterozygosity

• a way to introduce new desirable traits

example of inbreeding

royal families, hemophilia

outbreeding in plants

most plants cross pollinate and are therefore natural out breeders

Founder effect definition

loss of genetic variation when a very small number of individuals from a larger population establish a new colony

how does the Founder Effect occur?

due to migration or geographic isolation

what does the founder effect do for a population?

• the gene pool may be quite different from that of the original population

• eventually, the founder population can become a new species

• potential for rapid changes in a colony’s gene frequency suggests the founder effect is an important driving force in the evolution of new species

Example of the founder effect

• The cheetah​

• It is hypothesise that about 10,000 years ago due to climatic change a major extinction of large vertebrates occurred.  All but the small group of cheater died out forcing close family relatives to mate with each other​

• Recent genetic analysis with mtDNA shows an extremely low genetic diversity​

• Cheetah show signs of inbreeding depression​

• About 5% of cheetah survived to adulthood​

convergent evolution

process during which species that are not closely related to each other independently evolve similar kinds of traits to adapt to similar environments

• analogous structures

Divergent evolution

process in which a trait held by a common ancestor evolves into different variations over time

• homologous structures

Main types of speciation

• Geographic (allopatric): due to part of the population becoming isolated

• Sympatric: population occupies same geographical area

Geographic speciation

geographical speciation flow chart

Example of Geographical speciation

Galapagos finches. The Galapagos islands are volcanic islands that emerged from the sea relatively recently 3-4 million years ago​

• A group of finches is hypothesised to have landed on the island from the mainland driven by strong winds​

• on the island they remained permanently isolated from their point of origin and we're free to evolve because there was​

• an absence of pre-existing predators​

• no competition from other land birds​

• a variety of empty ecological nations​

Stages in the speciation process: division of habitat

division of food resources by trophic (feeding) specialization

• periods of food scarcity and growing population increased competition

• large number of open ecological niches promoted the development of feeding specialisations.

beak types

• grasping beaks- fruits and insects

• crushing beaks - eats seeds, ticks

• probing beaks - small to search in crevices

Reproductive isolation definition

A mechanism that prevents two or more species from exchanging genes (interbreeding) and producing fertile hybrids even though they are not geographically separated​

Reproductive isolation consequences

• breeding at different times of the year

• species-specific courtship behaviour

• adaptation of plants to different pollinators

• infertile offspring

Breeding at different times of the year

• Different species often have different mating seasons and plants flower at different times of the year which prevents mating opportunities​

• Examples​

• Grey headed parrot:  April to August  and Cape parrot:  August to February​

Species specific courtship behaviour

• Activity to signal sexual readiness​

• Prevents different species from interbreeding even though they territories overlap​

Species specific courtship behaviour examples

• Breeding display​

• Stridulating songs e.g. male cicadas​

• Secretion of pheromones​

• Breeding plumage​

Adaptation by plants to different pollinators

• Flowers designed so that only one specific pollinator can get to the pollen​

• Foul smelling flowers to attract flies​

• Dull coloured flowers (open at night) with a strong fruity or musty scent to attract mice and bats.​