Speciation Flashcards
What four types of species are there?
- biological species
- morphological species
- phylogenetic species
- ecological species
What is biological species?
It is reproductively isolated from others. Interbreeding individuals do not produce viable fertile offsprings.
Ex:
- dogs of all kinds reproduce viable offspring - so they are ONE species.
- dogs and foxes cannot interbreed, so they would be classified as different species.
What forms can reproductive isolation take up? (2)
Part of biological species
1) pre-zygotic barriers: it prevents sperm and egg from meeting.
Ex: (ALL IMPORTANT) Temporal - incompatible timing Habitat - incompatible habitats Gametic - incompatible sperm & egg Mechanical - incompatible structures Behaviour - incompatible courtship
2) post-zygotic barriers: reduced fitness of hybrid.
Ex:
hybrid viability - hybrids don’t survive
Hybrid sterility - hybrids can’t reproduce
1) What is morphological species?
2) what concepts of morphospecies has some problems?
1) Species that share a common set of physical characteristics, such as size, shape, colour etc.
2) CONCEPTS:
Cryptic species - species differing in traits other than morphology ex: oak bird and juniper titmouse.
Phenotypic plasticity - morphology changes with the environment, ex: growth of water cabbage
Polymorphic species - genetic variation in morphology in a species ex: jaguar colouration
Subjective traits: disagreement on characteristic of species. Ex: fossil identification
What is phylogenetic species?
Species that are the smallest monophyletic (group including most recent common ancestor and all of its descendants) group on the tree of life.
Extra: phylogenetic trees are made by identifying DNA sequences of each species.
What is ecological species?
Species that share a common set of ecological characteristics (environmental relationships suited to that species)
Ex: different species of lizards are adapted for different environments, resources and habitats.
What is subspecies?
Individuals that fall under the same species but with different characteristics.
Ex: the bengal, and Siberian tiger are subspecies from the same species of big cats, but different characteristics.
What is speciation?
The evolution of two or more species from a single ancestor.
EXTRA: the formation of new species requires different populations to develop new differences and this can’t happen is there is too much gene flow (recall gene flow increases similarities between populations).
What are two ways species can arise, and what two types are there for each?
1) allopatric speciation: a split into two geographical groups, divided by a barrier. The two groups diverge and become two species.
- ‘allo’ = other
TYPES:
-DISPERSAL: species can form when individuals disperse ( move from place of origin to new location) and colonize new habitats.
Ex: nene goose of Hawaii have evolved from Canadian geese, who dispersed from mainland and were then stranded. Over time evolutionary mechanism caused a divergence between the two populations and became a new species.
- VICARIANCE: species can form when existing populations are physically divided by a barrier (vicariance - population split by a geographic barrier)
Ex: formation of Amazon river isolated different populations caused a divergence into different species.
2) sympatric speciation: species diverge into two groups while in the same geographical area.
- ‘sym’= same
TYPES:
- DISRUPTIVE SELECTION: recall disruptive selection increases the amount of variation. So hybrids have lower fitness compared to the biological species.
Ex: apple flies and Hawthorne flies are able to find mates and food, but the hybrid of Hawthorne and apple flies have a harder time so lower fitness.
- MUTATION: Reproductive isolation can also arise when mutations changes the number of chromosomes.
Ex: genome duplication in plants.
