APS11006 Principles of Evolution- Freckleton Lectures Flashcards
Ancestral form of pigeons
Rock pigeon
Artificial selection
Variation in species generated by human-driven selection e.g. domesticated animals. Breeding and producing viable offspring with ‘ideal’ characteristics.
Evidence for evolution
- Fossil record
- Artificial selection
- Variation in space
- Homology
- Experimental evolution
- Observable evolution
Examples of animals that have been artificially selected
- Pigeons
- Dogs
Examples of crops that have been artificially selected
- Einkorn to ‘heritage’ wheat to ‘modern’ wheat
- Beta vulgaris and Beta maritima bred to become beetroot, chard and sugar beet
What sort of characteristics are bred for in crops?
- Easily grown
- Nutritious
Primula kewensis
- Hybrid between two existing, naturally occuring species (Primula verticillata and Primula floribunda)
- Realised through an accident
- Speciation through allopolyploidy
- Diploid 2n=36, while parents are 2n=18
- Therefore it cannot interbreed with either parent species
- Leads to ‘instant speciation’
Allopolyploidy
- Polyploidy is a condition in which an organism has more than two complete sets of chromosomes in every cell (>diploid)
- Allopolyploidy occurs when a polyploid offspring is derived from two distinct parental species
- (Primula kewensis is 4n compared to parents)
‘Instant speciation’
- Sympatric speciation which occurs by polyploidy
- Offspring is reproductively isolated and independent
What % of plant species are polyploids?
-40-70%
Sympatric speciation
Divergence of species by isolation within the same geographical location without a physical barrier
Spatial variation
- Variation in environment leads to variation in species
- Temperature change, predation and prey change etc lead to selection pressures
Biogeographical ‘rules’
- Bergmann’s rule
- Allen’s rule
- Lack’s rule
- Rensch’s rule
Bergmann’s rule
- Animals get larger further north
- SA:V is minimised, heat is lost at a lower rate
Allen’s rule
- Animals in colder climates have thicker limbs (and smaller appendages such as ears and tails)
- Small appendages reduces SA:V and thus heat loss
Lack’s rule
- The clutch size of each species has evolved to an evolutionary optimum
- May vary spatially
Rensch’s rule
Sexual dimorphism increases with average body size
Sexual dimorphism
Systematic difference in form between individuals of different sex in the same species
How do foxes in the US follow the biogeographical rules?
- Red foxes in north are larger, with thicker limbs and fur and smaller ears
- Red foxes in south have larger ears, thinner body, less fur
- Bergmann’s and Allen’s rules
Lepus arcticus vs Lepus californicus
- Arctic hares have small, fur-covered ears
- Desert hares have large ears
- Different coat colours
Ring species
- Situation in which two populations that do not interbreed are living in the same region and connected by a geographic ring of populations that can interbreed
- E.g. herring and lesser black-backed gulls
- Different characteristics for each species
How does fossil evidence exist?
- Fossils are contained within layers of sedimentary rock
- Older layers are covered by newer ones
- Also preserved animals e.g. in permafrost
What is Archaeopteryx an example of?
- Transitional form (birds and reptiles)
- Discovered through fossil records
Vestigial characters
- Structures that have no apparent function
- Serve as evidence of evolutionary relationships
- Whales possess pelvic bones, linking them to terrestrial mammals
Types of selection
- Natural selection
- Sexual selection
Natural selection
Descent with modification, driven by adaption to the local environment (change in organisms through time with inheritance of traits)
Basis for natural selection
- Variation
- Heritability
- Competition and fitness
Types of variation
- Discrete e.g. colour morphs in Biston betularia moths
- Continuous e.g. range of variation in banding intensity oh shells of cepaea nemoralis
Non-genetic variation
Over last 20 years, its recognised that there’s a form of non-genetic variation involving the modification of DNA throughout lifetime in response to environment which is inheritable. Epigenetics.
Is variation completely random?
No, has a deterministic genetic basis