evolution

Question 1

what is comparative anatomy and what does it include

Answer 1

• comparing body structures of organisms - similarities suggest they may share a common ancestor - embryology - homology - vestigial organs - analogous structures

Question 2

embryology

Answer 2

• all members of phylum chordata have a notochord, nervous chord and tail - looks at anatomical homologies not present in adults - similarities suggest that they share a common ancestor from which they evolved into different species - eg bird and human, have same features and look the same however as adults are no longer the same

Question 3

homology

Answer 3

• homologous structures - structural variations in different species - stem from a similar common ancestor - similar bones, number, position, infer common ancestor - limb has been modified to fit different ways of life - eg pentadactyl limb, have 5 components human, whales and bat all have the same structure but they have formed differently and evolved to suit our environment

Question 4

vestigial organs

Answer 4

• different structures that no longer serve a purpose - lost effectiveness - whale pelvic bone, remains of a structure (human tailbone) evolved into having no legs therefore no need for a tailbone but the bone is still present in whales

Question 5

analogous structures

Answer 5

• structures with similar functions from different origins (not a common ancestor) - eyes in octopus and mammals same function and structure however no common ancestor
• hte wings of a bat and the wings of an insect

Question 6

what is comparative genomics

Answer 6

• comparison of genome sequences (bases)

Question 7

comparative genomics - DNA

Answer 7

• nuclear DNA has the same 4 bases - DNA for a gene varies by the base sequence - sequences can be found using the sanger method - sequence varies from species to species - more similarities = common ancestor - bioinformatics uses computers to analyze bases - computers store and produce large amount of data

Question 8

comparative genomics mtDNA

Answer 8

• found in the mitochondria - varies in base sequence from species to species - only inherited from the mother - mutates faster then DNA - more similarities = common ancestor - very different = not related - all humans descended from mitochondria eve - assumes mutation rate is constant 1 every 2000 years - if 2 mutations therefore common ancestor was 4000 years ago

Question 9

hybridization

Answer 9

• indicates the degree of relatedness - measures how hard it is to separate DNA 1. extract DNa from 2 species, cut into fragments 2. heat DNA to 86C to unzip the DNA 3. cool, mix, join complementary strands 4. slowly reheat until hybrid dna unzips 5. record the separation temperature 6. the higher the temperature the more base pairing therefore the more related

Question 10

comparative genomics - proteins

Answer 10

• proteins are long chains of amino acids - the more similar the more closely related - similarities depend on number of mutations - eg hemoglobin, cytochrome C hemoglobin: 146 amino acids long - chimpanzee has 0 differences (common ancestor) - dogs have 15 differences cytochrome C: all animals have it for respiration - number of differences reflect evolutionary distance - chimp 0 differences - cow 10 differences

Question 11

fossils

Answer 11

• preserved parts of a dead organism which shows organisms have changed over time and there are intermediate forms - intermediate forms - fossil sequence
• show past life
• can be dated or assigned a time period
• allows us to follow changes

Question 12

intermediate fossils

Answer 12

• punctuated equilibrium - states that species remain fairly stable but may change swiftly to a new species - eg archaeopteryx - well developed teeth, long tail unlike living birds - 3 finger claws unlike fused fingers of living birds

Question 13

fossil sequence

Answer 13

• gradualism - assumes evolution occurs at a steady and slow rate - reveals many intermediate states between an organisms ancestral form calling transitional forms - possibly to observe gradual change over time as their shape or size transition to different forms - eg the evolution of the horse - contains numerous transitional forms - environmental transition from forrest to grassland drove many changes observed in the fossil record - reduction in two number, increased size of check teeth, increased body size

Question 14

what does a phylogenetic tree show

Answer 14

• relatedness/ similarities - relationships between different groups of taxa - common traits

Question 15

node on a diagram

Answer 15

the T junction where one species split into 2

Question 16

clade on a diagram

Answer 16

the 2 species that came off the one

Question 17

forming of fossils

Answer 17

permineralisation: minerals in water replace hard structures trace fossils: footprints amber: tree resin ice: frozen

Question 18

comparative / relative dating

Answer 18

• used to determine the age of fossils relative to others near by sedimentary rock: layers in the ground, oldest at bottom

Question 19

absolute dating

Answer 19

• assigns a numerical age to the fossil radiometric dating: based on rates of decay electron spin resonance: measures electrons amount of radiation increases with time , therefore can determine age luminescence: measures light when it is emitted from a mineral when it is heated

Question 20

fossil record

Answer 20

• incomplete and rare - many extinct species - shows changes over time

Question 21

fossils form best when

Answer 21

• rapid burial - alkaline soils - anaerobic conditions

Question 22

divergent evolution

Answer 22

• pattern of evolution where differences between groups of organisms accumulate that leads to speciation - have common ancestors but show different structures

Question 23

adaptive evolution

Answer 23

• organisms diversify rapidly from an ancestoral species into multiple new forms

Question 24

convergent evolution

Answer 24

unrelated species evolve similar adaptations

Question 25

macroevolution vs microevolution

Answer 25

macro is large changes over a long period of time, evolution of new species that can no longer breed eg marsupials micro is small changes, within a population due to mutation, selection, gene flow and genetic drift eg types of dogs