BIO 3052 EVOLUTION PROCESSES Flashcards
Species
- transcend time, not populations or individuals
- a group of actually, or potentially, interbreeding natural populations that are reproductively isolated from other such groups
Hybrids
The result of a cross between individuals of two different species or subspecies
Population
Refers to individuals of the same species living in a particular area and sharing the same gene pool
Gene pool
All alleles of a gene within a population
Crossing over
The exchange of genetic material between homologous chromosomes
Inheritance
Characteristics that pass from one generation to the next
Interbreeding
Each individual that lives in a species carries a unique combination of genotypes, and every time sexual reproduction takes place, there is a mixing of genetic material. Interbreeding means exchanging genetic material (species context)
Give examples of hybrids
-crosses between two closely related species
-dog with dingo, grey wolf, coyote
-rarer for animals and a product of circumstance, eg, no other potential mates nearby or being held captive
-often, (plants & animals) hybrids may be sterile which means genes will be lost from gene pool when they die
Ring species
-type of cline
-connected series of neighboring populations, each of which can interbreed with closely sited populations, but no interbreeding occurs anymore between individuals from the two ‘ends of the ring’
Cryptic species
-Morphology of individuals is very similar or identical, so they look alike but no inbreeding.
-Gene pools are not shared so dealing with different species
-When analysing DNA, conclude that there was only one species.
-CRYPTIC SPECIES (hidden or obscure)
Explanations of cryptic species
Speciation has already broken down interbreeding but not enough time has passed for this to have become apparent as different phenotypes.
Deme
Local population that can interbreed with another population and therefore share the same gene pool
Speciation
Formation of new species
Gene pool of large Māhoe population.
North and South island saddlebacks
Barriers to interbreeding :
- Geographic : North island vs South island
- Different calls
- Different plumage
Hector’s and Māui’s dolphins
Barriers to interbreeding :
- Geographic : North island vs South island
Barriers to interbreeding
-pre-zygotic barriers (favoured over) & could be a key factor in stopping interbreeding between different species
-post1zygotic barriers
Pre-zygotic barriers
-Habitat isolation : organisms within a population become physically seperated
-Temporal isolation : being active at different times of the day, breeding at different times of the year
-Behavioural isolation : like courtship behaviour in birds, songs and calls, beak size, brightest plumage ( if anything is not right mating will not occur)
-Mechanical isolation : incompatibility of sexual organs prevents mating
-Gametic isolation : gametes of one individual do not survive inside the body of the other individual, or gametes fail to fuse properly
-Geographic isolation : isolation where there are physical barriers between closely related species such as mountains, rivers, the sea or altitude
Post-zygotic barriers
-Reduced hybrid viability : hybrids form but die (offspring die young or does not develop)
-Reduced hybrid fertility : hybrids form but are sterile
-Hybrid breakdown : hybrids may be fertile and reproduce successfully, but then their offspring are either infertile or they die young
Geographic isolation
•Physical barriers such as mountains, rivers, sea and altitude- important driver of speciation
•distinguis between sympatric speciation and allopatric speciation
•Speciation occurs because because of demes becoming geographically isolated.
Sympatric speciation
-two seperate species form from one species in the same place
-arise when vacant niches in habitat can be exploited as selected from different alleles in parents population.
-seasonal, behavioural, and mechanical isolation are most likely causes
Allopatric speciation
When populations of one species become isolated from each other and change into seperate species over time
Allele frequency
Proportion of all copies of a gene being of a particular type/version
What does loss of alleles mean
Loss of alleles means loss of genetic variation.
Can affect long-term survival chances that a population and species might have