Speciation: Origin of Species Flashcards
Define “population”
Members of a single species living and reproducing within a single area.
Define “species”
A group of organisms that can freely interbreed under natural conditions and are reproductively isolated from other species.
What is the role of mutation? (relate to natural selection)
To create/introduce new alleles, contributing to natural selection by creating favourable/unfavourable alleles to be selected for/against to help the species survive/exploit certain features in an environment.
Steps of Speciation (5)
- Genetic Variation within a population
- Geographical isolation between populations (barrier)
- Natural selection, subject to different selection pressures
- Mutation, accumulation of beneficial mutations
- Reproductive Isolation interbreeding is impossible
What is a Deme?
A deme is a subpopulation that can freely interbreed with other subpopulations since there is no limited gene flow (populations remain same species)
What is a Cline?
A cline is a pattern of gradual variation between individuals over a geographical area (geneotype/phenotype) interbreeding with immediate neighbours
What are Reproductive Isolating Mechanisms (RIMS)?
Any factor that stops members of the same/different species from interbreeding acting as a barrier to gene flow.
What are the two modes of Speciation?
Allopatric and Sympatric
What is allopatric speciation?
When geographical barriers separate the population
1. prevention of gene flow
2. Reproductive isolation -> speciation (significant genetic differences)
What is Sympatric Speciation?
Formation of a new species without geographical isolation (separation in the same area). Some become dependent on certain features of an environment whereas other may not.
What are the types of Postzygotic RIMs?
- Hybrid Inviability (offspring are unable to survive/develop normally -die early)
- Hybrid Sterility (hybrid reaches maturity but is infertile - no viable gametes)
- Hybrid Breakdown (can reproduce but subsequent offspring are have reduced reproductive fitness)
What are types of Prezygotic RIMs? (6)
- Geographical isolation (occupy different areas)
- Ecological isolation (occupy/exploit different habitats within an area)
- Behavioural isolation (different courtship behaviours)
- Temporal isolation (Breeding behaviours at different times)
- Mechanical isolation (external reproductive structures are incompatible)
- Gametic isolation (incompatibility of gametes)
What is Polyploidy?
A heritable condition of possessing more than 2 complete sets of chromosomes (errors during cell division)
selected for - offspring have traits from both species (able to thrive in multiple environments)
What is Autoploidy?
Multiplication of the genome of a single species.
Non-disjunction of homologous chromosomes during meiosis (diploid gametes)
What is Alloploidy?
Two different species produce an infertile hybrid
Chromosomes from different parents are non-identical, typically cannot pair up during meiosis
