BIO120 #1 (1-6) Flashcards
(40 cards)
1
Q
Evolution
A
- genetic change over time.
- species evolve at different rates depending on natural selection.
2
Q
Gradualism and Uniformitarianism
A
- evolution is an overall gradual process (although there are different rates of natural selection).
- Lyell: Uniformitarianism ○ Nature was not static.
○ The current mechanisms of change were the same thousands of years ago. - shown by the fossil record.
3
Q
Speciation
A
- splitting of lineages
- creating separate species.
4
Q
Common Ancestry
A
- each species has a common ancestor.
- descended with modification.
- examined retroactively by looking at the fossil record, phylogeny or DNA sequences.
- proof: transitional forms (Tiktaalik).
5
Q
Natural Selection
A
- Requires genetic variation in the population.
- environment selects for traits
- Individuals with adaptations survive, reproduce and pass on adaptations to their offspring.
- change over time.
6
Q
Strength of Natural Selection
A
- ○ Strong (when adapting to a new environment) = faster evolutions.
○ Weak (same environment) = slower evolutions.
7
Q
Genetic drift
A
- random changes to allele frequency in pop’n (e.g. scooter running over an ant).
- pronounced in smaller pop’ns.
- non-selective change.
- only way for neutral genes/pseudogenes to evolve.
- decreases variation in pop’n
8
Q
Genetic Bottleneck
A
- env’ntal change leads to a significant decrease in pop’n.
- decreased genetic variation.
- e.g. endangered species found only in zoos.
9
Q
Founder Effect
A
- group of individuals that leave the main pop’n to reside somewhere else.
- different mix of alleles than original pop’n => new gene pool.
- finches and colonizing
10
Q
Ordering the Fossil Record
A
- deeper layers (older) = organisms that are less complex; less similar to current species.
- shallower layers (younger) = more complex; more similar to current species.
11
Q
Dating Fossils
A
- carbon dating or uranium dating by measuring the radioactive decay.
12
Q
What the Fossil record shows
A
- evidence that complexity directly corresponded with evolution (Darwin discovered).
- evidence of common ancestors (transitional forms).
- evidence of gradual evolution within a species.
13
Q
Transitional forms/missing links
A
- evidence of common ancestors
- fill in the gaps between two dividing species (speciation).
14
Q
How did flight evolve?
- what is useful about half a wing?
A
- transitional form (archaeopteryx): feathers before flight.
- “tree down”
- “ground up”
-
15
Q
Lamarck’s Theory
A
- use/disuse
- characteristics developed during lifetime will be passed down to offspring.
- genetic info can be passed from DNA to proteins (and not in reverse).
16
Q
Vestigial
A
- a hereditary trait that doesn’t perform the same function for which it evolved.
- changed use: penguin’s wings to flippers.
useless: kiwi bird’s wings. - reason: env’nt selects against the trait.
17
Q
Atavism
A
- anomaly: a random, accidental re-expression of a silenced ancestral gene/trait.
- occur in individuals, not across pop’ns (like vestigial).
18
Q
Pseudogenes
A
- dead, unexpressed genes that we carry from our ancestors.
19
Q
Palimpsests (traces) in Embryo
A
- traits that evolved earlier are developed earlier in embryo.
- traits that evolved later are developed later in the embryo.
- new ones are layered onto the ancestor’s.
20
Q
Why do different continents have similar species (look and act similar)?
A
- convergent evolution: different species but same environmental pressures = look/act similar.
21
Q
How did Darwin predict that humans would have closely related ancestors in Africa?
A
using the co-occurence of living descendants and fossil ancestors.
- our closest relatives reside in Africa.
22
Q
Oceanic Islands
A
- rose from the ocean as a volcano, reef
- missing species: species that are unable to colonize using long-distance dispersal.
- native species: species able to colonize using long-distance dispersal, are very diverse (adaptive radiation) and are most similar to species on the closest mainland.
23
Q
Continental Islands
A
- broke off from the mainland
- have diverse species.
- old continental islands: broke off from mainland when there were ancient species–there is a low level of diversity that allow for strange animals to evolve and radiate the many niches (e.g. giant flightless birds).
24
Q
Diversity
A
- Chance: (e.g. dispersal–winds etc., mutations)
- Lawfulness (e.g. new env’nts = adaptive radiation)
25
Biogeography results
- geographically close organisms resemble each other
- species with similar env'nt pressures become similar (convergent).
- geographically isolated places allow for strange organisms.
26
Genotype
- the genetic makeup
| - the alleles combos inherited for a gene (AA, Aa etc.)
27
Phenotype
- appearance of organism
28
Genome
- all DNA (including coding genes and pseudogenes)
29
Effects of Mutations
- beneficial: increase survival (becomes more common in pop'n)
- creates variation.
- deleterious: decreases survival (becomes less common in pop'n).
=> lethal brings fitness to zero.
30
Independent assortment
- chromosomes line up combos in meiosis.
| - creates variation.
31
Recombination
- overlapping of chromosome homologous pairs during meiosis
| - creates variation.
32
Pre-Mendel Heredity
- blending of genes to create offspring
| - individual parent traits are lost.
33
Mendel: Nature and Inheritance
- inheritance determined by genes.
- each organism receives two copies of alleles (one from each parent randomly).
- organisms form gametes that contain one type allele.
34
Discontinuous inheritance model
- Mendel inheritance
- link genotype to phenotype
- genes majorly affect phenotype (dominant and recessive).
35
Continuous inheritance model
- cannot directly link genes to phenotype.
- multiple genes + multiple env'ntal factors = phenotype.
- many genes with individual small impact
- quantitative inheritance: the more genes, the more phenotype options.
- multiple loci (genes from different places) are involved in creating the phenotype.
36
Types of Natural Selection
- positive natural selection: (adaptation) traits selected for (eventually trait will be fixed in the pop'n) => decreases variation.
- negative natural selection: the removal of alleles that make one less fit => decreases variation.
- balancing selection: maintaining 2 types of genes (heterozygous advantage) => causes variation.
37
Migration and Diversity
- gene flow
- within pop'n: increases diversity
- overall pop'n: becomes one pop'n; less diversity.
38
Classical school
- most of selection is negative selection
- therefore: lower heterozygosity & lower polymorphism.
- wild types (selection does not favour diversity).
39
Balance School
- a lot of natural selection favours heterozygosity.
- therefore: higher heterozygosity & higher polymorphism.
- selection favours diversity.
40
sexual selection
- increases chance of getting a mate.
