Lectures 18-20

Question 1

biological evolution

Answer 1

evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

Question 2

natural selection vs artificial selection

Answer 2

natural selection produces a great biological diversity whereas artificial selection produces varieties of organisms such as improved crops and livestock
natural selection happens naturally, but selective breeding only occurs when humans intervene

Question 3

microevolution vs macroevolution

Answer 3

Microevolution is the process by which organisms change in small ways over time. Macroevolution refers to larger evolutionary changes that result in new species.

Question 4

species vs population

Answer 4

species is a group of similar individuals who interbreed with each other whereas population consists of individuals of a particular species, in a specific region at a certain time

Question 5

Fossils

Answer 5

The remains or traces of ancient organisms left in sedimentary rock (most common), or ice, sand or other places.
Gives you information about the morphology of organisms that lived in the past.

Documents (some of) the biodiversity of the past.
Get some information on where & when they lived
& when there were extinctions or arrival of new species (using the morphological species concept)

Limitations
Rare that organisms form fossils & mostly of hard-bodied organisms
“The known fossil record is biased in favor of species that existed for a long time, were abundant and widespread in certain kinds of env’ts, and had hard shells, skeletons, or other parts that facilitated their fossilization” p554, 2nd Cdn ed

Info about external but rarely internal form

Evolution can occur without morphological change (ex behavioural); and morphological change can occur without evolution (ex height & diet)

Question 6

Molecular Homologies

Answer 6

You will see molecular similarities if organisms are related by a common ancestor: the more recent the common ancestor, the more sequence similarities (in DNA and/or amino acid sequence of proteins) you’d expect
Similarity that the two organisms share at the molecular level due to common ancestry

Question 7

Homologous features vs vestigial structures

Answer 7

Homologous features: organisms with similar structures, but different functions, hypothesized to have a common ancestor
Compare with analogous structures resulting from convergent evolution

Vestigial structures: structures occasionally become vestigial as species adapt to different modes of life. Ex Kiwi bird doesn’t fly, but still has wings

Question 8

Evolution vs natural selection

Answer 8

evolution (the process) and natural selection (the mechanism).

Question 9

Convergent evolution

Answer 9

Organisms with separate ancestries adapt in similar ways to comparable environmental demands: have analogous structures

Question 10

Analogous vs homologous structures

Answer 10

Homologous structures are similar physical features in organisms that share a common ancestor, but the features serve completely different function

Analogous
Analogous structures are features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature

Question 11

selective pressures

Answer 11

Any reason for organisms with certain phenotypes to have either a survival benefit or disadvantage

Question 12

genotype vs gene pool

Answer 12

Gene pool: the total number of alleles present in a population; the set of all genes, or genetic information in any population of a particular species (not necessarily of all the species in the whole world, but rather in that one population under study). It includes all genes and combinations of genes (sum of the alleles) in the population.
A genotype is an individual’s collection of genes

Question 13

5 conditions necessary for genetic equilibrium to be maintained.
Hardy-Weinberg Principle

Answer 13

For a population that is not evolving ie is at genetic equilibrium:

the frequencies of alleles and genotypes in a population’s gene pool remain constant from generation to generation

A sexually reproducing population will be at genetic equilibrium (not evolving) if all 5 conditions to genetic equilibrium are met
natural selection not occurring
mating is random
no net mutations
large population (avoid genetic drift)
no migration between populations

Question 14

5 factors that can change a gene pool. (adaptive or not)

Answer 14

Natural selection (adaptive: adapting to the environment)
Includes sexual selection (adaptive non-random mating)

Non-adaptive:
Non-random mating that’s not adaptive
Genetic mutations
Genetic drift: Bottleneck, founder effect
Gene flow

Question 15

gene flow, founder effect and bottlenecking

Answer 15

Gene flow: transfer of alleles between populations; usually this refers to exchange of alleles between members of the same species (ex grizzly bears in BC and in Alaska), through sexual reproduction, but gene flow (horizontal gene flow) can also occur between different species.

Bottleneck: a type of genetic drift where some members of population do not pass on their genes by not fault of their own. The population [and its genetic diversity] is severely reduced as a result of a natural disaster, predation, or habitat reduction.

Founder effect: a type of genetic drift where individuals that start a new population will have their alleles more represented in the new population.

A bottleneck effect is when there is a very noticeable reduction in population size for a minimum of one generation time. A founder effect is when a few individuals move to a new region and start a new colony of limited genetic variation.

Question 16

selective pressures act on the individual, but evolution acts on populations.

Question 17

advantages and disadvantage of the 3 definitions (concepts) of a species

Answer 17

Biological species concept
1. Biological species concept emphasizes reproductive isolation
Reproductive isolation: is the existence of biological factors (barriers) that impede 2 species from producing viable, fertile offspring
Reproductive isolation restricts gene flow b/w 2 species.
This is the legal definition of a species under the Endangered Species Act.
Limits to this definition:
Can’t be used for species that reproduce asexually or that are extinct.
To know if reproductive isolation exists, need to know all the breeding partners of the species in question, but can’t know for sure who breeds with who in nature. (see bear example)
Gene flow can sometimes occur between distinct species (see hybrids)

Morphological traits species concept
A species is a group of organisms with similar structure (morphology) & behavior.
Applies to sexual & asexual species but relies on subjective criteria
it does not distinguish between species that are actually produced by convergent evolution and are not really closely related. It also does not group individuals of the same species that would happen to be somewhat morphologically different like in color or size

Common ancestor: phylogenetic species concept
The smallest group of individuals that share a unique common ancestor and who all possess a unique set of morphological or genetic traits.
Applies to sexually & asexually reproducing species,
BUT
it can be difficult to determine the degree of difference required to indicate separate species: how much of a difference in DNA sequence is enough to say they are different species?

Question 18

Allopatric speciation

Answer 18

Habitat isolation occurs: pre-zygotic reproductive barrier b/w groups: Glaciers move, rivers change direction, mountains form, islands form etc… separating 1 population (1 species) into 2 or more populations of that 1 species

Each population exposed to different selective pressures, genetic drift, +/or mutation that cause micro-evolution

Eventually, 1 or both populations undergo enough genetic changes that results in the formation of permanent reproductive barrier (bio species concept)