evolution Flashcards
1
Q
what is comparative anatomy and what does it include
A
- comparing body structures of organisms - similarities suggest they may share a common ancestor - embryology - homology - vestigial organs - analogous structures
2
Q
embryology
A
- 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
3
Q
homology
A
- 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
4
Q
vestigial organs
A
- 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
5
Q
analogous structures
A
- 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
6
Q
what is comparative genomics
A
- comparison of genome sequences (bases)
7
Q
comparative genomics - DNA
A
- 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
8
Q
comparative genomics mtDNA
A
- 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
9
Q
hybridization
A
- 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
10
Q
comparative genomics - proteins
A
- 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
11
Q
fossils
A
- 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
12
Q
intermediate fossils
A
- 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
13
Q
fossil sequence
A
- 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
14
Q
what does a phylogenetic tree show
A
- relatedness/ similarities - relationships between different groups of taxa - common traits
15
Q
node on a diagram
A
the T junction where one species split into 2
