chapter 15 - evidence for evolution

Question 1

what is the human genome project

Answer 1

• completed in 2003
• fully sequences human DNA
• scientists have sequenced preserved samples that are over millions of years old

Question 2

what is annotation

Answer 2

• identification of genes in a DNA sequence, uses the start and stop codons to identify a gene

Question 3

what is DNA and code (comparative studies)

Answer 3

• all living things contain DNA and four bases (ACGT), indicates we have evolved from a common ancestor
• variation occurs (mutation, natural selection and genetic drift etc.)
• comparison of ERV’s and mtDNA
• code: DNA code varies between different species

Question 4

what is speciation

Answer 4

• species that are more distantly related have more differences in DNA
• species more closely related share a greater portion of DNA

Question 5

differences in DNA

Answer 5

• humans and chimpanzee (1.2%), 98% similarity humans have 23 chromosome pairs chimps have 24
• chimpanzee and gorilla (1.2%)
• human and gorilla (1.6%)
• chimpanzee and orangutang (1.8%)
• human and orangutang (2.4%)
• gorilla and orangutang (2.4%)

Question 6

what is hybridisation

Answer 6

• act or process of mating organisms of different species to create a hybrid (offspring relating from cross between parents of different species / subspecies)
  1. species 1 and 2, DNA is heated, dented DNA from species mixes
  2. DNA cooled, some H bonds do not reform in hybrid DNA due to the difference in base sequences
  3. the hybrids are reheated, greater temperature difference to temp. needed to denature the original sample the less similar the DNA strands are

Question 7

what is junk DNA / ERV’s (comparative studies)

Answer 7

• junk: chromosomes containing non-coding sequences of bases in DNA, no apparent function or purpose
• more closely related species have more junk sequences in common
• ERV: retrovirus that has become part of an organisms genome and is present in every cell of the body (8% of human genome)

Question 8

retrovirus vs ERV

Answer 8

• retrovirus: stores genetic material as RNA not DNA and are not functional
• insertion: retrovirus enters host cell, convert RNA into DNA via reverse transcriptase, DNA is inserted into host cell DNA and copies are made
• become endogenous if it inserts into gametes
• all subsequent generations will have ERV in same position
• 16 instances where ERV’s match between humans and chimps
• short arm of chromosomes 1,9,6 and 10 and long arm of chromosome 9

Question 9

what is a phylogenetic tree

Answer 9

• graphical representation of an evolution to show how different groups diverged over time
• reveals that some have more recent common ancestor than others (share more ERV’s)

Question 10

what is mitochondria / mtDNA

Answer 10

• organelle where aerobic respiration takes place, contains mtDNA
• mtDNA: small, circular molecules, 5-10 in each organelle, contains 37 genes (24 = code for tRNA, 13 = code for enzymes in cellular respiration
• cells have high mitochondria, (~500-1000 mtDNA, therefore ~16500 base pairs), easier to trace ancestry, less is required, many copies in each cell

Question 11

inheritance of mtDNA

Answer 11

• both sperm and ova contain mtDNA
• sperm: only have enough to provide energy to swim
• mtDNA is only inherited from the mother

Question 12

mutation of mtDNA

Answer 12

• mutation: higher rate of mutation than nDNA
• significant difference between mtDNA today in comparison to original female ancestor (amount of mutation is roughly proportional to time passed)

Question 13

ancestry of mtDNA

Answer 13

• trace migration routes of ancient populations
• mapping evolutionary relationships between humans and related species and comparing those within a species (siblings, cousins)
• neanderthals: last common ancestor of humans (600000ya), interbred with homo sapiens

Question 14

protein sequences and amino acids (comparative studies)

Answer 14

• long chains of up to 20 kinds of AA, biochemical techniques sequence AA in protein
• comparisons between species (different AA / arrangement)
• AA: represented by 3 letter code, in sequencing represented by 1 letter

Question 15

types of comparative studies in biochemistry

Answer 15

• DNA, ERV’s / junk DNA, mtDNA and protein sequences

Question 16

ubiquitous proteins

Answer 16

• present in all species, carry out same basic functions no matter where they are found (independent)
• cytochrome C: essential step in cell resp. changed very little over millions of years
• human cyt. C: 104 AA, 37 of these have been found in same position in all species
• cyt. C descended from a primitive microbe that existed more than 2000 million ya
• cyt. C is exactly same in humans, chimps and gorillas,
  1 AA diff. in patas monkeys
• alpha / beta chains (haemoglobin): humans and chimps identical seq. differ by 1 in gorillas and gibbons by 3
• delta chain (haemoglobin): humans, chimps and gorillas differ by 1 and gibbons by 2

Question 17

types of comparative anatomy

Answer 17

• comparing the structural features of related animals to determine the degree of similarity between them (similarities in structure = common ancestor)
• embryology, homologous structures, vestigial organs

Question 18

comparative embryology

Answer 18

• comparing the very early stages of development of organisms
• evidence for evolutionary, comparing embryonic stages = remarkable similarity
• fish, reptile, bird, pig and human: all have gill pouches / arches (all vertebrate began with fish), divergence into amphibians, reptiles, birds and mammals
• humans: embryonic gill slit = eustachian tube, tonsils and thyroid gland
• all species: well developed tail is present, a two chambered heart and similar brain development

Question 19

comparative homologous structures

Answer 19

• similar structure with different functions
• forelimbs: same bone appears in various forms, feet (amphibians, reptiles), wings (bats / birds), leg (horse, lion), flipper (whale, seal), hand (humans)
• human and gorilla have v similar leg muscles (common ancestor)

Question 20

comparative vestigial organs

Answer 20

• structures of reduced size, no function, common in vertebrate species
• humans: ~90, muscles to move ear, nicitating membrane (3rd eyelid, small pink bit inner eye), pointed canine (tearing), wisdom teeth (raw meat), nipples (males), hair on body, appendix (culture of good gut bacteria), coccyx (tail), pyramidalis bone (above pubic bone, tensing of abdomen), muscles at tips of hairs (insulation, goosebumps)

Question 21

what is geographical distribution

Answer 21

• evidence for evolution, distribution of related species
• aus: before humans, >100 species of kangaroos / koala
• monotremes: egg laying mammals (echidna / platypus), found in aus and island near png. (bread in isolation)
• darwin / finches: finches on mainland different to those on galapagos islands (migration, no competition), natural selection / favourable characteristic (lots of food source, beaks changed, 13 types)
• geographic isolation: lemurs (madagascar), new world monkeys (america), old world monkeys (asia / africa)
• > predicted that human fossils would be found in africa (humans = gorillas / chimps), later found them there

Question 22

evolution and creation

Answer 22

• genesis tells creation story of bible, believed to be real
• catholics see story as symbolic, explain origins of life to people before scientific knowledge of 21st century
• acceptance of evolution does not prelude a belief and faith in god

Question 23

what is bioinformatics

Answer 23

• multidisciplinary field that combines all areas of biological science with computer science, statistics and applied mathematics to help understand biological processes
• use of computers to describe the molecular components of living things
• very useful in tracing evolution, by measuring DNA rather than through physical taxonomy or physiological observations
• annotation (genes have recognisable start and stop codons)

Question 24

what is comparative genomics

Answer 24

• genome sequences of different species are compared
• able to identify regions of similarity and difference
• identifies genes preserved among species and genes that result in unique characteristics
• revealed extreme similarity as well as diversity of gene composition in different evolutionary lineages