Evolution Flashcards
What are the two common forms of natural selection?
Stabilizing selection: Average phenotypes have a selective advantage over extremes (bellcurve distribution)
Directional selection: When one extreme has a selective advantage over the average phenotype (curve can become skewed to the left or the right). Disruptive selection occurs when directional selection skews to both the left extreme and right extreme (eg. very small feathers and very big feathers)
What is a cline?
A gradient of variation in a species across a geographical area
What is genetic drift and when does it normally occur?
The random change in frequencies of alleles or genotypes in a population.
Genetic drift normally occurs when a small population is isolated from a large population. Since the allelic frequencies in the small population may be different from the large population, the two populations may evolve in different directions.
What are sympatric and allopatric species/populations?
What are some factors that lead to allopatric ‘speciation?’ (8)
Species/populations that live together (sympatric) or apart (allopatric)
- habitat difference
- difference breeding times
- mechanical differences (genitalia aren’t compatible)
- behavioural specificity
- Gametic isolation (fertilization can’t occur)
- Hybrid inviability (hybrid zygote dies)
- Hybrid sterility
- Hybrid breakdown (fertile hybrid that produces infertile offspring)
Define the following:
Homologous structures:
Analogous structures:
Vestigial structures:
Homologous structures: Part has same origin in different species, but different function.
Analogous structures: Similar function, but arise from different embryological structure
Vestigial structures: Useless organs (in owner) that are homologous with organs that are useful in other species
Give the seven taxonomic classes
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Korean people can often fry gaseous stones…
What are the 6 features of chordates?
- A notochord
- Pharyngeal gill slits
- Hollow dorsal nerve cord
- Segmented anatomy
- Internal skeleton (endoskeleton)
- A tail (at some point in development)
Give five features of vertebrates
- Vertebral column
- Well developed sensory and nervous system
- Ventral heart with a closed vascular system
- Liver, endocrine organs and kidneys
- Cephalization
Why would a freeze-resistant frog want to have ample liver glycogen stores rather than a high tissue glucose concentration?
A high tissue glucose concentration would keep the frog alive for a short period, liver glycogen could sustain glucose levels however, with glycogenolysis in the liver.
A species of lizards has a fleshy ‘dewlap’ that is sometimes colourfully decorated. To determine the significance of UV reflectance by the dewlap, it would be most useful to compare the behaviour of:
A. Lizards responding to flashing of normal dewlaps versus treated dewlaps that absorb UV
B. The five lizard species under illumination by red light only
A. Lizards responding to flashing of normal dewlaps versus treated dewlaps that absorb UV
To determine the significance of UV reflectance by the dewlap, it would be most useful to compare the response of lizards to dewlaps that reflect UV light. If the reflectivity of the dewlap is kept as the only variable it can be determined whether a correlation exists between the lizard’s behaviour and the reflectivity of the dewlap with which the lizards were flashed
Why do microfilament lengths not change when the sarcomere of muscles shortens in a muscle contraction?
The - ends of the microfilaments are capped by Z lines, and the + ends are capped by another protein.
Within a sarcomere, the microfilament length remains stable. Because one end of the microfilament is anchored in the Z line, actin monomers are prevented from being added to or subtracted from that end. This rules out the possibility of treadmilling, therefore to retain a stable length, both ends of the microfilament must be capped.
The shark intestine is shorter and less convoluted than that of mammals. The shark intestine, however, is not hollow, but contains a spirally folded mucous membrane (the spiral valve). The spiral valve is most likely analogous in function to the mammalian:
A. Liver and pancreas
B. Stomach mucosa
C. Intestinal villi and convolutions
D. Pyloric valve
The function of the intestines is to move nutrients from its cavity across its lining and into the blood stream. The speed with which this can be accomplished depends on how much surface is available for this process. The amount of surface area can be increased by folds (eg. shark) or projections (villi in mammals).
Which of the following would be the best evidence that the two species are related?
- Similar outward appearance
- Similar motility
- Analogous structures
- Homologous structures
Homologous Structures
Homologous structures originate from the same part of the embryo in different species allowing a comparison of evolutionary history.
Homology is the existence of shared ancestry between a pair of structures, or genes, in different species. A common example of homologous structures in evolutionary biology are the wings of bats and the arms of primates.
