Lecture 7 - evidence for evolution Flashcards
What is evidence for evolution?
- artificial selection
- variation in space
- fossil record
- homologs
- experimental evolution
- observable evolution
What is artificial selection?
- human-generated evolution (human driven selection
- breed species with selected, desired characteristics to produce an offspring with desirable characters
How have pigeons been artificially selected?
for pigeon racing
- a range of different types of pigeon have been bred, based on physical characteristics, colours or even behaviour
How have dogs been artificially selected?
morphologically they are very variable
How have crops been artificially selected?
ancestral crops were selected for desirable characteristics
- these have been amplified through natural selection:
- e.g. eichorn –> heritage wheat –> modern wheat
How has Beta vulgaris been artificially selected?
selection has led to sugar beet, beetroot & chard all deriving from this one species
How has artificial selection generated a new species?
- new species that is a hybrid between 2 existing ones
- parental species are Primula verticula & Primula floribunda
- speciation through allopolyploidy: the hybrid of the 2 parent species has doubled chromosome number
- leads to ‘instant speciation
- quite common in nature - 40-70% of plant species are polyploids
Why was artificial selection used by Darwin in the origin of species?
- species are not immutable - change is possible
- accumulation of small changes
- directional change through selection
What are biogeographical rules?
they tell use that there are common adaptive responses of organisms in different places
What is Bergmann’s rule?
animals get larger further North
What is Allen’s rule?
animals in colder climates have thicker limbs
What is Lack’s rule?
the clutch size (total eggs a bird lays per each nesting attempt) of each species has evolved to an evolutionary optimum
What is Rensch’s rule?
sexual dimorphism increases with average body size
Are changes evident in space?
- differences in foxes found between the North of America & the South is evidence of evolution. The foxes in the North have more fur, as it is colder
- same with rabbits
What is the difference between a Herring gull vs Lesser black-backed gull?
- at different ends of a ring species
- an examples of evolution, as it shows the intermediate species that have been created due to differences in environmental conditions
What is the difference in bears in different areas?
e.g. brown bear & polar bear - polar bear has white fur, which is useful for local environmental conditions
What is the difference in different species of sparrow, as an example of hybrid speciation?
Italian sparrow is a hybrid of house sparrow & Spanish sparrow
- Italian sparrow occurs in an area of overlap of House & Spanish sparrows
- almost certainly arose as a hybrid between them
- now a distinct species (independent breeding populations)
How can the fossil record be used for mapping evolution through deep time?
- fossils are contained within layers of sedimentary rock
- older layers covered by new ones
- can trace inter-relationships 4 transitionary forms
- also preserved animals - e.g. in permafrost
- fossils allow us to map the evolutionary process and look at links between species
- started by mapping the evolution of elephants using fossils
What is the evolution of horses?
- used teeth and foreleg structures to map how things like diet and locomotion had changed throughout the years
- allows for palaeobotanical reconstruction based of tooth structure
Transitional forms in the fossil record demonstrate the evolutionary links between major groups
What is an example of link between reptiles, dinosaurs & birds?
Archaeopteryx
Describe the Jawbone found in Svalbard permafrost
- the evidence was a combination of bone (fossil) & DNA
- bone was 130-111,000 years old
- sequencing of DNA allows comparison of different modern bears
- jawbone’s DNA was found in between polar bear & brown bear
How are homologs evidence for evolution?
Evidence from morphology
- homologous characters are traits that are inherited from a common ancestor
- although they are inherited, they may now serve different functions
- the existence of homologs shows that different groups have evolved from common ancestors
- as well as show where they have diverged
How are birds & bats an example of homologs as evidence for evolution?
- both can fly & have wings
Bats - mammals
Birds - birds - the limbs of bats & birds are homologous as they inherited these from a common ancestor
- they each have 2 pairs of limbs ‘arms’ & ‘legs’
- however, the differences in structure mean that at the same time, their wings are non-homologous (analogous)
What are similarities & differences between birds, bats & humans?
The forelimbs of birds, bats & humans show homologs - they are comprised of the same bones - but the wings of bats & birds are structurally very different - they are therefore not homologous
What are vestigial characters?
- Extant organisms have structures that serve no function
- their presence serves as evidence of evolutionary relationships
- also provides evidence of evolutionary change
- e.g. Whales possess pelvis bones, linking them to terrestrial mammals
What is universal homology?
underlying homology as we share DNA
What is experimental evolution and how can it be used as evidence for evolution?
- using fast-reproducing organisms, it is possible to demonstrate evolution under lab conditions - e.g. until COVID-19, Richard Lenski has been able to proliferate for 73,500 generations of E. coli
- there were 12 founding populations and all these showed the same evolutionary response to the conditions
- experimentally-imposed-stresses lead to evolutionary changes that can be measured
- can test evolutionary theories
