BIO120 #1 (1-6)

Question 1

Evolution

Answer 1

• genetic change over time.

- species evolve at different rates depending on natural selection.

Question 2

Gradualism and Uniformitarianism

Answer 2

• 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.

Question 3

Speciation

Answer 3

• splitting of lineages

- creating separate species.

Question 4

Common Ancestry

Answer 4

• 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).

Question 5

Natural Selection

Answer 5

• 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.

Question 6

Strength of Natural Selection

Answer 6

• ○ Strong (when adapting to a new environment) = faster evolutions.
  ○ Weak (same environment) = slower evolutions.

Question 7

Genetic drift

Answer 7

• 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

Question 8

Genetic Bottleneck

Answer 8

• env’ntal change leads to a significant decrease in pop’n.
• decreased genetic variation.
• e.g. endangered species found only in zoos.

Question 9

Founder Effect

Answer 9

• 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

Question 10

Ordering the Fossil Record

Answer 10

• deeper layers (older) = organisms that are less complex; less similar to current species.
• shallower layers (younger) = more complex; more similar to current species.

Question 11

Dating Fossils

Answer 11

• carbon dating or uranium dating by measuring the radioactive decay.

Question 12

What the Fossil record shows

Answer 12

• evidence that complexity directly corresponded with evolution (Darwin discovered).
• evidence of common ancestors (transitional forms).
• evidence of gradual evolution within a species.

Question 13

Transitional forms/missing links

Answer 13

• evidence of common ancestors

- fill in the gaps between two dividing species (speciation).

Question 14

How did flight evolve?

- what is useful about half a wing?

Answer 14

• transitional form (archaeopteryx): feathers before flight.
• “tree down”
• “ground up”

-

Question 15

Lamarck’s Theory

Answer 15

• 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).

Question 16

Vestigial

Answer 16

• 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.

Question 17

Atavism

Answer 17

• anomaly: a random, accidental re-expression of a silenced ancestral gene/trait.
• occur in individuals, not across pop’ns (like vestigial).

Question 18

Pseudogenes

Answer 18

• dead, unexpressed genes that we carry from our ancestors.

Question 19

Palimpsests (traces) in Embryo

Answer 19

• 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.

Question 20

Why do different continents have similar species (look and act similar)?

Answer 20

• convergent evolution: different species but same environmental pressures = look/act similar.

Question 21

How did Darwin predict that humans would have closely related ancestors in Africa?

Answer 21

using the co-occurence of living descendants and fossil ancestors.
- our closest relatives reside in Africa.

Question 22

Oceanic Islands

Answer 22

• 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.

Question 23

Continental Islands

Answer 23

• 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).

Question 24

Diversity

Answer 24

• Chance: (e.g. dispersal–winds etc., mutations)

- Lawfulness (e.g. new env’nts = adaptive radiation)

Question 25

Biogeography results

Answer 25

• geographically close organisms resemble each other
• species with similar env’nt pressures become similar (convergent).
• geographically isolated places allow for strange organisms.

Question 26

Genotype

Answer 26

• the genetic makeup

- the alleles combos inherited for a gene (AA, Aa etc.)

Question 27

Phenotype

Answer 27

• appearance of organism

Question 28

Genome

Answer 28

• all DNA (including coding genes and pseudogenes)

Question 29

Effects of Mutations

Answer 29

• 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.

Question 30

Independent assortment

Answer 30

• chromosomes line up combos in meiosis.

- creates variation.

Question 31

Recombination

Answer 31

• overlapping of chromosome homologous pairs during meiosis

- creates variation.

Question 32

Pre-Mendel Heredity

Answer 32

• blending of genes to create offspring

- individual parent traits are lost.

Question 33

Mendel: Nature and Inheritance

Answer 33

• inheritance determined by genes.
• each organism receives two copies of alleles (one from each parent randomly).
• organisms form gametes that contain one type allele.

Question 34

Discontinuous inheritance model

Answer 34

• Mendel inheritance
• link genotype to phenotype
• genes majorly affect phenotype (dominant and recessive).

Question 35

Continuous inheritance model

Answer 35

• 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.

Question 36

Types of Natural Selection

Answer 36

• 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.

Question 37

Migration and Diversity

Answer 37

• gene flow
• within pop’n: increases diversity
• overall pop’n: becomes one pop’n; less diversity.

Question 38

Classical school

Answer 38

• most of selection is negative selection
• therefore: lower heterozygosity & lower polymorphism.
• wild types (selection does not favour diversity).

Question 39

Balance School

Answer 39

• a lot of natural selection favours heterozygosity.
• therefore: higher heterozygosity & higher polymorphism.
• selection favours diversity.

Question 40

sexual selection

Answer 40

• increases chance of getting a mate.