Evolution

Question 1

define evolution

Answer 1

change in genetic makeup of the population

• constant propogation of new variations in genes of a species some with an important adaptive advantage

Question 2

what is lamarchian theory of evolution

Answer 2

• new organs or changes in existing ones arose because of the needs of the organism
• amount of change based on use or disuse of the organ
• theory based on acquired characteristics DISPROVED bc only changes in the DNA of cells can be inherited
• changes aquired in individuals life occur to somatic cells: not passed to offspring

Question 3

explain darwins theory of natural selection

Answer 3

• pressures in environment select for the most fit to survive and reporduce
• number of a particular species equipped with beneficial traits allow it to cope effectively with the environment will rpoduce more offspring than those with unfavourable genetic traits

*natural selection: nature selects the best set of parents for next generation

Question 4

what are the basic agents leading to evolutionary change

Answer 4

Overpopulation: more offspring are produced than can survive, insufficient resouces to support

Variations: offspring show differences in characteristics compared to those of their parents , mutations can cause variations (some beneficial but most harmful)

Competition: developing population must compete for nexessities of life. many young must die and number of adults in populations ramains constant from generation to generation

Natural selection: organisms have variations that can give advantages over other members in the species. allows them to survive over others

inheritance of variations: those that surive to adulthood reproduce and transmit favourable variations or adaptations to offspring -> genes gradually dominate the gene pool

Evolution of new species: accumulatino of variations result in significant cahnges in gene pool, can say new species has evolved, physical changes were perpetuated or selected by environmental conditions

Question 5

explain specification

Answer 5

• evolution of a new species: can interbreed with eachother but not with members of other species
• gene flow is not possible between diff species
• different selective pressures act upon gene pool of each group causing then to evolve independently

*factors leading to specification include: changes in environemnt, migration to new environment, adaptation to new env, natural selection, genetic drift and isolation

Question 6

what are demes

Answer 6

• form before specification: small local populations within species
• members of deme resemble on another more closely than they resemble members of other demes (closely related genetically bc mating within deme occurs more frequently)
• if deme becomes isolated then selection may occur -> no genetic flow between groups
• any new mutations or combination of genes are confined within the deme and maintined in the isolated population

* if gene pools within the species become so genetically differnt that two individuals cant mate to produce fetile offspring then two different species have developed

Question 7

what is phylogeny

Answer 7

• evolutionary history
• can be visualized with a branching tree

Question 8

what is convergent evolution

Answer 8

• two species from different ancestors develop similar traits
  ex: sharks and dolphins resemble eachther physically despite belonging to different classes of vertebrates

*evolve certain similar features to adapt to environmental conditions

Question 9

what is parallel evolution

Answer 9

• similar to convergent but when a more recent ancestor can be identified

* similar traits with a recent ISH common ancestor still diff species

Question 10

what is divergent evolution

Answer 10

• species with a shared ancestor develip differing traits due to dissimilarities between their environments
• ex polar bears vs black bears developing diff coats to mimic environemnt
• overtime additional changes have occurs and cant cross breed the bears

Question 11

what is adaptive radiation

Answer 11

• emergence of a number of lineages from a single acestral species

**single species may diverge into a number of distinct species

• differences are due to a distinct lifestyle or niche
• ex: a single finch species underwent asaptive radiation resulting in 13 diff species some on the same island. this minimzed competition amoung the birds and enabled the emergence of firmly established environemntal niches

Question 12

what is gene frequency

Answer 12

• decimal fraction representing the presence of an allele for all members of a population that have a particular gene
• in basic mendilian genetics onyl 2 alleles exist for a given trait (dom and recessive)

p = dominant and q = recessive

p + q =1

Question 13

what is the hardy weinberg principle

Answer 13

• gene freq is relative to the freq of a particular allele
• when gene frequency of a population is not changing the population is not evolving IF

*the population is large, no mutation in gene pool, mating between individuals is random, no net migration in or out of population and genes are equally sucessful at reproducing

• under these ideal conditions p² + pq + q² =1
• p² (TT), pq (Tt), q² (tt)

Question 14

If frequency of the dominant allele is 80% what are teh F1 genetype frequencies of crossing two heterozygoes

Answer 14

1 = p² + 2pq + q²

• if dom = 80% recessive = 20%
• TT = 0.8 x 0.8 = 0.64 (64%)
• Tt = 2(0.8 x 0.2) = 32%
• tt (0.2 x 0.2) = 0.4 (4%)

Question 15

what are the factors of microevolution

Answer 15

* no population can be represented indefinitly by the hardy weinburg principle bc these ideal conditions not realistic

• real populations have unstable gene pools and migrating populations
• agents of microevolution include

1. Natural selection: genotypes w/ favourable variations are slected and freq of their genes inc in gene pool
2. Mutation: gene mutations change allele freq in a population shifing the gene equilibria by introducing additional alleles (mutations can be favourable or detrimental)
3. Assortive Mating: if mates not randomly chosenbut selected accorign to phenotype of proximity the relative genotype ratios will be affected
4. Genetic Drift: changes in composition of gene pool due to chance (more pronouced in small popultions, can be called founder effect
5. Gene Flow: migration between populations resuling in loss or gain of genes (changes gene pool)

Question 16

what are fossil records

Answer 16

• evidence of evolution, generally sound in sedimentary rocks, tar pits, ice or amber
• petrification = process in which minerals replace the cells of an organism
• imprints= impressions left by an organism
• molds form hollow spaces in rocks as the organism in rock decays

casts formed by mineral deposited in molds

Question 17

what is comparative anatomy

Answer 17

• evidence of evolution
• can be homologous or anologous structures

Homologous structures

• same basic anatomical features and evolutionary origins
• demonstrate similar evolutionary patterns w/ late divergence of form due to differences in exposure to evolutionary forces
• origins and anatomical features may be similar but functions of the strucutre may not be
• ex wings of bat and flipper of whale, forelegs of horses and arms of humans

Analogous structures

• simliar functions but diff evolutionary origins and entirely diff patterns of development
• wings of a fly and wings of bird are analogous, superificial resemblance that cant be used as a basis for classification

Question 18

what is comparative embryology

Answer 18

• stages of developemnt of embry resmeble the stages in an organisms evolutionary history
• human embryonic development passes thru stages demonstarting common ancestry
• two layer gastrula is similar to strucutre of the hydra, a cnidarian
• three layer gastrula is similar to structure of flat worm
• Gill slits in embryo indicate common ancestry with fish
• the earler the stage at which developemnt begins to diverage the more dissimilar the adult organism will be

Question 19

what is comparative biology

Answer 19

• evidence of evolution
• most organisms have same basic needs and metabolic processes
• similarity between enzyems involved in processes suggests all organisms must contain some DNA sequences in common
• the more recent the ancestor the greater the similarity of chemical constituents
• chemical similarity of the blood of different organisms parallels the evolutionary patters
  ex: blood of chimps is more similar to humans than fish, indicates less time has elapsed since the divergence of humans and chimps than chimps and fish

Question 20

what are vestigal structures

Answer 20

• evidence of evolution
• structures with no known use/ current function but has some ancestral function
  ex: appendix small and useless in huamns but assists in digestion of cellulose in herbivores
• in humans tail is reduced to useless boens (coccyx) at base of spine

Question 21

what is the role fo geographic barriers

Answer 21

• new species generally accompanied with migration to lessen intraspecific competition, species begin to differ and reproductive isolation would be maintained even if barrier is removed
  ex: Marsupials (pouched animals) parralleled developemnt of placental animals, goegraphic barrier (australia) protected pouched animals and the developemnt of uniquely australian marsupicals

Question 22

what is the heterotroph hypothesis

Answer 22

• first forms of life not able to synthesize own nutrients, depending on outsidesources for food
• primitive seas contained inorganic and organic compounds (salts, methanes, ammonia, hydrogen water) and energy present in form of heat, electricity, solar radiation, radioactivty
• building blocks and energy may have lead to synthesis of simple organic molecules (sugat, amino acids, pruiens, pyrmidines), these mol combined to form supply of macromolecules

Question 23

evidence of organic synthesis

Answer 23

• UV radiation, heat or a combination and a mix of methane, hydrogen, amminia and water and result in formation of complex organic molecules
• these gases were ciruclated past electrical dischanges from tungten electrodes, liquid in apparatus contained a variety of organic compounds

Question 24

explain formation of primitive cells

Answer 24

• collodial protein mol tend to clump together forming coacervate droplets (cluster of collodial mol surrounded by shell of water)
• droplets tend of absorb and incorperate substances of surrounding environment
• small percentage of droplets with favourable characteristics may have eventually developed into first primative cells (probably possesed nucleic acid polymers and became capable of reproduction)

Question 25

explain the development of autotrophs

Answer 25

- primative heterotrophs slowly evovled complex biochemical pathways allowing them to use a wider variety of nutrients - evolved anaerobic respiratory process to conv nutrients into energy - developed to porduce own organic compounds from substances in surroundings - pioneer autotrophs developed primitive photosynthetic pathways capturing solar energy and using ti to synthesize carbohydrates from CO2 and water

Question 26

explain development of aerobic respiration

Answer 26

- primitive autotrophs fixed CO2 during synthesis of carbohydrates and released oxygen as waste - addition of O2 to atmosphere converted it from a reducing to an oxidizing zone - soma O2 conv to ozone which functions to block high energy radiation - once O2 became a signifcant portion of atmosphere both heterotrophs and autotrophs evolved the biochemical pathways of aerobic respiration - now equilibrium exists beetween oxygen producing and consuming organisms

Question 27

what are teh 4 catagroies of living organisms

Answer 27

- autotrophic anerobes (chemosynthetic bacteria) - autotrophic aerobes (green plants and phytoplankton) - heterotrophic anaerobes (yeasts) - heterotrophic aerobes (amoebas, earthworms, huamns)