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.
what are the characteristics of filicinophytes?
- have roots, leaves & short non-woody stems
- leaves usually divided into leaflets and curled up in a bud
- have vascular tissue
- spores are produced in sporangia, usually on the underside of the leaves.
what are the characteristics of coniferophytes?
- roots, leaves and woody stems.
- leaves are usually narrow with thick waxy cuticle.
- have vascular tissue
- seeds are produced in cones. seeds are produced from ovules on the surface of the scales of female cones. male cones produce pollen.
what are the characteristics of angiospermophytes?
- have roots, leaves and stems.
- stems of flowering plants that develop into shrubs and trees are woody.
- have vascular tissue
- seeds are produced from ovules inside the ovaries, which are part of the flower. The fruits then develop from the ovaries and disperse the seeds
what are 5 vertebrae?
- mammals
- birds
- reptiles
- amphibians
- fish
what are the characteristics of mammals?
- 4 pent limbs
- lungs with alveoli
- internal fertilization/give birth to live young/mammary glands secret milk
- hair & teeth
what are the characteristics of birds?
- 4 pent limbs + 2 limbs modified as wings
- lungs with parabronchial tubes
- internal fertilization / hard shells around eggs
- feathers & beak but no teeth
what are the characteristics of reptiles?
- 4 pent limbs
- lungs with extensive folding
- internal fertilization / soft shells around eggs
- dry scaly impermeable skin
what are the characteristics of amphibians?
- 4 pent limbs
- simple lungs with small folds
- external fertilization / protective jelly around eggs
- soft, moist permeable skin
what are the characteristics of fish?
- fins
- gills for gas exchange
- external fertilization
- scales grow from the skin with a single gill slit + swim bladder for buoyancy
what are 7 animal phyla?
- prifera (sponges)
- cnidaria (corals, jellyfish)
- platyhelmintha (flatworms)
- annelida (earthwoms, leeches)
- mollusca (snails, octopus)
- arthropoda (ants, scorpions)
- chordata (fish, birds, mammals)
what are the characteristics of prifera?
- no symmetry
- no segmentation
- no mouth, no anus
- pores through body
what are the characteristics of cnidaria?
- radial symmetry
- no segmentation
- mouth, no anus
- stinging cells
what are the characteristics of platylhelmintha?
- bilateral symmetry
- no segmentation
- mouth, no anus
- flattened body
what are the characteristics of annelida?
- bilateral symmetry
- very segmented
- mouth and anus
- bristles often present
what are the characteristics of mollusca?
- bilateral symmetry
- non-visible segmentation
- mouth and anus
- shell may be present
what are the characteristics of arthropoda?
- bilateral symmetry
- segmented
- mouth and anus
- exoskeleton
what are the characteristics of chordata?
- bilateral symmetry
- segmented
- mouth and anus
- notochord
what is a clade?
a group of organisms that evolved from a common ancestor
where does evidence for which species are part of a clade come from?
- the base sequences of a gene or
2. the corresponding amino acid sequence of a protein
what is an analogous structure?
- features of different species that are similar in function but not necessarily in structure
- are a result of convergent evolution
- e.g. bird and bat wings
what is convergent evolution?
- when unrelated organisms evolve similarities when adapting to similar environments
