unit 5 Flashcards
what is evolution
the cumulative change in the heritable characteristics of a population over time
how do fossil records provide evidence for evolution?
- show changes over time in many organisms.
- fossilized organisms are different from existing ones; they were not identical but had similarities with existing organisms.
how does selective breeding provide evidence for evolution?
- shows that artificial selection can cause evolution.
- by breeding members of a species with a desired trait, the trait’s frequency becomes more common in successive generations
- e.g selective breeding of cows to produce more milk.
how do homologous structures provide evidence for evolution?
- HS within different species suggest common ancestry.
- evolution of HS by adaptive radiation explains similarities in structure when there are differences in function.
- many bones in the limbs are common to a number of species - suggests that these have evolved from one common ancestor.
- e.g the pentadactyl limb of humans, bat wings and whale fins
what is adaptive radiation?
the evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat.
what is gradual divergence?
populations of a species can gradually diverge into separate species by evolution.
what is speciation?
the evolutionary process by which two related populations diverge into separate species
how does speciation occur?
- within a population of any species there is genetic variation
- this variation is continuous and follow a normal distribution curve as the rate of change is gradual
- if two populations of a species become geographically separated then they will likely experience different ecological conditions
- overtime, the 2 populations will adapt to the different environmental conditions and gradually diverge from one another
- the degree of divergence will depend on the extent of geographical separation and the amount of time since separation occurred
what causes genetic variation?
- mutation
- sexual reproduction
- random fertilization
- meiosis
how does natural selection occur?
- overproduction of offspring causes competition for resources/struggle for survival
- offspring show variation (caused by 4 factors) = some have characteristics that give them an advantage
- these individuals are more likely to survive & reproduce
- through inheritance of these advantageous characteristics the frequency of them become greater in the next generation
- leads to changes to population as a whole = evolution
what is an example of adaptive radiation?
- the variety of beak types seen in the finches of the Galapagos Islands
- these finches have specialised beak shapes depending on their primary source of nutrition (e.g. seeds, insects, nuts, nectar)
what are the 3 domains?
- archaea: no nuclear membrane. RNA & biochemistry distinct from bacteria
- bacteria: no nuclear membrane
- Eukaryota: animals, plants & fungi. have nuclear membrane
what is the hierarchy of taxa?
- kingdom (animalia & plantae)
- phylum
- class
- order
- family
- genus
- species
what are 4 plant phyla?
bryophytes (e.g. moss)
filicinophytes (ferns)
coniferophytes (shrubs & trees)
angiospermophytes (flowering plants)
what are the characteristics of bryophytes?
- no roots, but similar structures called rhizoids
- simple leaves and stems
- no vascular tissue
- spores are produced in capsules. The capsule develops at the end of a stalk.
