Chapter 9 - Evolution

Question 1

Define evolution:

Answer 1

The change in genetic makeup of a population with time

Question 2

What can explain evolution?

Answer 2

The constant propagation of new variations in the genes of a species, some of which impart on an adaptive advantage

Question 3

In regards to evolution, what are all living things?

Answer 3

All living things, past and present, are descendants from a single common ancestor
- Each arose as a priest result of some genetic alteration in the species that lived before them

Question 4

How to evolutionary changes occur?

Answer 4

They occur slowly over a long period of time

Question 5

What are the two theories of evolution?

Answer 5

1) Lamarckian

2) Darwin

Question 6

Describe the Lamarckian Theory of Evolution:

• Proposed by?
• What was the amount of change based on?
• What was the theory or use and disuse based on?
• Give an example

Answer 6

Proposed by Jean-Baptiste Lamarck and held that new organs or changes in existing ones arose because of the needs of the organism

• The amount of change was based on the use or disuse of the organ
• The theory of use/disuse was based on any useful characteristic acquired in one generation was thought to be transmitted to the next
• Ex. Giraffe neck

Question 7

What was the flaw with the Larmarckian Theory of Evolution? Why?

Answer 7

Genetics disapproved the theory of acquired characteristics
- Only changes in the DNA of sex cells can be inherited, whereas, changes acquired during an individual’s life are changes in somatic cells

Question 8

Describe Darwins Theory of Evolution:

• What is fitness?
• Natural selection?

Answer 8

Pressures in the environment select for the organism most fit to survive and reproduce

• Fitness is the ability to survive and reproduce
• Essentially, species equipped with beneficial traits will cope effectively with the environment and pass them down to offspring which become increasingly prevalent in the gene pool
• Natural selection is nature selecting the best parents for the next generation

Question 9

What are the 6 aspects of Darwin’s Theory?

Answer 9

1) Overpopulation: More offspring produced than can survive, thus, food/air/light/space are insufficient to support the entire population.
2) Variations: Offspring show variations in characteristics compared to parents; some beneficial, most harmful.
3) Competition: Developing population must compete for necessities of life; many young die and the number of adults within each population remain constant from generation-generation.
4) Natural Selection: Species that have variations that give them an advantage over other members of the species (i.e. adaptations); based on “survival of the fittest”.
5) Inheritance of the Variations: Individuals that survive live to adulthood to reproduce and transmit these favourable variations to their offspring; favourable traits gradually dominant the gene pool.
6) Evolution of New Species: Over generations of natural selection, favourable changes are perpetuated in the species and the accumulation of favourable changes results in significant changes in the gene pool to say that a new species has evolved; perpetuated or selected via environmental conditions.

Question 10

What is speciation?

Answer 10

The evolution of a new species which are groups of individuals that can interbreed freely between each other but not with members of its own species.

Question 11

When is gene flow impossible?

Answer 11

Between different species.

Question 12

How do groups evolve independently?

- What are the factors?

Answer 12

When different selective pressures about upon the gene pools of each group.
- Factors include - genetic variation, change in environment, migration to new environment, adaption to new environment, natural selection, genetic drift, and isolation all lead to speciation

Question 13

What is a deme?

Answer 13

Small, local populations that occur before speciation.

Question 14

What happens if demes become isolated? How? What does geographic isolation of a population do?

Answer 14

Speciation may occur

• When groups are isolated from one another there is no gene flow, therefore differences arise from mutations or new combinations of genes maintained
• Over time, mating may become impossible because the gene pool are significantly different (two different species)
• Results in genetic and eventually reproduction isolation

Question 15

What is phylogeny?

Answer 15

Understanding the evolutionary relationships amongst species alive today
- Branching tree

Question 16

What is convergent evolution?

Answer 16

When two species from different ancestors develop similar traits

Question 17

What is parallel evolution?

Answer 17

Similar to convergent evolution but occurs when a more recent ancestor can be identified

Question 18

What is divergent evolution?

Answer 18

Occurs when species shared a common ancestor develop different traits due to dissimilarities between their environment.

Question 19

What is adaptive radiation? What is the difference between them?

Answer 19

The emergence of a number of lineages from a single ancestral species
- Differences n their niche

Question 20

Define population:

Answer 20

Includes all the members of a particular species inhabiting a given location.

Question 21

Define gene pool of a population:

Answer 21

The sum total of all the alleles for any given trait in a population.

Question 22

Define gene frequency:

- Equation

Answer 22

The decimal fraction representing the presence of an allele for all members of a population that have this particular gene.

p + q = 1

Question 23

What is the Hardy-Weinberg Principle?

Answer 23

Under the following ideal conditions, a certain equilibrium will exist amongst all of the genes in a gene pool will hold true:

1) The population is very large
2) No mutations affect the gene pool
3) Mating between individuals in the population is random
4) There is no net migration of individuals into/out of the population
5) The genes in the population are all equally successful at reproducing

Question 24

What is the Hardy-Weinberg Equation? What is it used for?

Answer 24

p^2 + 2pq + q^2 = 1

Used to determine the gene frequencies in a large population in the absence of micro=evolutionary change

Question 25

What is micro-evolution?

Answer 25

No population can be represented indefinitely by the HW-Equilibrum because idealized conditions do not exist in nature
- Unstable gene pools and migrating populations

Question 26

What are the 5 conditions of the HW-Population?

Answer 26

1) Natural Selection: Genotypes with favourable variations are selected through natural selection, and the frequency of favourable genes increases within the gene pool; genotypes with low adaptive values tend to disappear
2) Mutation: Gene mutations change allele frequencies in a population, shifting gene equilibria by introducing addition alleles; gene mutations can either be favourable or detrimental for offspring
3) Assortive Mating: If mates are not random but selected according to criteria, the relative genotype ratios will be affected and will depart from the prediction of HW-equlibrium.
4) Genetic Drift: Refers to changes in the composition of the gene pool due to chance; tends to be more pronounced in small populations where it is sometimes called (founder effect).
5) Gene Flow: Migration of individuals between populations will result in a loss/gain of genes, thus changing the composition of a population’s gene pool.

Question 27

What are fossils records? What do they tell us? Where are they generated?

Answer 27

Direct evidence of evolutionary change

• Present preserved remains of an organism
• Generated in sedimentary rocks

Question 28

What are the 5 different types of fossils?

Answer 28

1) Amber - Fossil resin of trees
2) Petrification - Process by which minerals replace cells of organism
3) Imprints - Impressions left by organism
4) Molds - Form hollow spaces in rocks as organisms decay within
5) Casts - Formed by mineral deposited in molds

Question 29

What are some significant fossil finds?

Answer 29

1) Paleozoic Era: The trilobite (primitive arthropod) was discovered.
2) Mesozoic Era: Dinosaurs
3) Wooly Mammoth found in Siberian Ice
4) Saber-tooth tiger preserved in asphalt tar pits
5) Insects preserved in amber

Question 30

What are homologous vs. analogous structures?

Answer 30

1) Homologous: Same basic anatomical features and evolutionary origins, similar evolutionary patterns with late divergence of form due to differences in exposure to evolutionary forces, origin and anatomical features are similar their functions may not be
- Ex. Wings of a bat

2) Analogous: Similar function but different evolutionary origins and entire different patterns of development
- Ex. Wings of a fly vs. wings of a bird

Question 31

What is comparative embryology? Compare the two vs. three layer gastrula? What happens if the development diverges early on? Describe different evidence of evolution:

Answer 31

The stages of development of the embryo resemble the stages in an organism’s evolutionary history

• Human embryo passes through stages that demonstrate common ancestry with other organisms
• Two layer gastrula is similar to structure of the hydra (cnidarian)
• Three layer gastrula is similar to structure of flatworm
• Earlier the age at which development diverges, the more dissimilar the adult organism will be
• Gill slits in embryo indicate common fish ancestry
• Avian embryo has teeth, shared ancestry with reptiles
• Larvae of some molluscs resemble annelids
• Human embryos possess tail, like other mammals

Question 32

What is comparative biochemistry? What suggests similarities? Why can we suggest all organisms descended from a single common ancestral form?

Answer 32

Most organisms have the same basic needs and metabolic processes - require same nutrients, contain similar cellular organelles, and energy storage (ATP)

• Similar enzymes suggests that all organisms must contain some DNA sequences in common
• More recently organisms shared a common ancestry, the reader the similarity of their chemical constituents and genetic info = allowing us to conclude that all organisms descended from a single common ancestral form

Question 33

What are vestigial structures? Give some examples:

Answer 33

They have no known current function but apparently had some ancestral function

• Humans - appendix
• Humans - tail
• Horses - splints on their toes
• Python - legs

Question 34

What is species multiplication generally accompanied by? What do emerging geographic barriers increase?

Answer 34

Migration to lessen infraspecific competition

• Separation by emerging geographic barriers increases likelihood of genetic adaptions on either side of the barrier; each population can evolve specific adaptions to the environment it lives in addition to accumulating neutral changes - these adaptation remain unique to population in which they evolve
• With time, interbreeding becomes impossible between the populations and reproductive isolation occurs even if the barriers were removed

Question 35

What is the heterotroph hypothesis?

Answer 35

First forms of life lacked ability to synthesize own nutrients and thus required preformed molecules
- These organisms were heterotrophs

Primitive seas contain inorganic/organic compounds (salts, methane, ammonia, water, hydrogen)
- Energy present in form of heat, electricity, solar radiation, cosmic rays, and radioactivity

These building blocks and energy may have lead to the synthesis of simple organic molecules (sugars, amino acids, purines, pyrimidines) dissolved in the “primordial soup” which combined to form macromolecules.

Question 36

What is the evidence of this organic synthesis?

Answer 36

Stanley L. Miller wanted to demonstrate the application of the types of energy used mixed with hydrogen, methane, and water that would result in complex organic compounds:
- When the 4 gases were circulated and passed electrical charges through, the liquid produced had a variety of organic compounds including urea, hydrogen cyanide, acetic acid, and lactic acids

Question 37

How were primitive cells formed?

Answer 37

Collodial protein molecules tend to clump together which form coacervate droplets that absorb and incorporate substances from the surrounding environment

• The droplets possess definite internal structure, making is highly likely that such droplets developed on Earth
• They are not living but do possess properties associated with living organisms
• Unstable system; a few droplets may have possessed favourable characteristics and developed into the first primitive cells (possessing nucleic acid = reproduction)

Question 38

How did autotrophs form?

Answer 38

Primitive heterotrophs slowly evolved complex biochemical pathways allowing them to utilize a wide variety of nutrients

• Evolved repiratory processes to convert nutrients to energy - however, they required nutrients at faster rate than they could synthesized
• Life would not exist if autotrophic nutrition did not develop; production of organic compounds
• Pioneer autotrophs developed photosynthetic pathways to capture solar energy and synthesize carbohydrates from CO2 and H2O

Question 39

How did aerobic respiration occur?

Answer 39

Primitive autotrophs sized CO2 during synthesis of carbohydrates and released O2

• O2 in the atmosphere converted atmosphere from reducing to oxidizing one
• Molecular oxygen converted into ozone that blocks high-energy radiation allowing living organisms to develop
• O2 come a major component of Earth’s atmosphere allowing heterotrophs and autotrophs to evolve the biochemical pathways of aerobic respiration

Question 40

What are living organisms divided into?

Answer 40

1) Autotorphic anaerobes = Chemosynthetic bacteria
2) Autotrophic aerobes = Green plants & photoplankton
3) Heterotrophic anaerobes = Yeasts
4) Hetertrophic aerobes = Amoeba, earthworms & humans