AOS 4 Flashcards
1
Q
what is mass extinction
A
when a larger-than-normal number of groups become extinct on regional and global scale
* evolutionary opportunity for other species to thrive and diversify
2
Q
evidence for evolution
A
- fossils
- biogeographical distribution
- comparative
- anatomy - structural morphology
- embryology - developmental biology
- molecular homology - DNA and amino acid sequences
3
Q
conditions that favour fossilisation
A
- rapidly buried
- protected from scavengers
- prevented from decomposition by low oxygen levels and low tempratures
- organisms having hard structures (won’t decompose as rapidly)
4
Q
process of fossilisation
A
- an organism dies and is rapidly buried
- protected from scavengers
- prevented from decomposition by low oxygen levels + low temperatures
- continued deposits of sediments bury it more and more deeply
- over time the molecules in the organism (usually the hard parts) are replaced by minerals from groundwater
- gradually, the weight of the overlying sediments compresses the original sediment layer so that it becomes rock
- over time the rock is eroded, uplifted through the movement of tectonic plates or excavated
5
Q
timeline of life on earth
A
- prokaryotes
- first unicellular eukaryotes
- first multicellular eukaryotes
- first vertebraes (jawless fish)
- first insects
- first land plants
- first amphibians
- first ferns
- first reptiles
- first conifers
- first dinosaurs
- birds
- first mammals
- first flowering plants
- primates
- humans
6
Q
mineralised/petrified fossils
A
organic material of a structure replaced by minerals
7
Q
mold fossils
A
- form when a mineralised/petrified fossil dissolves and leave an impression of the original
- these can be filled in to make cast fossils
8
Q
trace fossils
A
- form when traces of activity are buried before they are erased and turn into rock
- eg footprints, teeth marks, scats (faeces)
9
Q
purpose of fossil record
A
- the fossil record reveals that over time changes have occurred in the types of organisms living on this planet
- provides evidence in support of the prediction that ancestral species will appear before the species that descend from them
10
Q
fossil/faunal succession
A
- based on the premise that strata accumalates in chronological order
- fossils in lower strata are older than fossils closer to the surface
- fossils in lower strata are less complex than strata closer to surface
11
Q
relative dating
A
- sedimentary rocks form in layers (strata)
- newer layers are at the top and the older layers are at the bottom
- can determine relative age from that (as in newer or older - not the specific time)
12
Q
index fossils
A
- index fossils can be used to determine the relative ages of rock strata anywhere in the world
- presence of index fossils in rock strata in widely separated regions of the world can identify these rocks as having the same age.
- must be
- abundant
- distributed worldwide
- existed for only a short period of time
13
Q
transitional fossils
A
- can tell us about major changes - evidence of evolution
- is the fossilised remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group
- e.g: archaopteryx - dinosaur and modern birds (claws on wings + feathers)
14
Q
absolute dating techniques
A
- radiometric dating is the most common way to find the actual age of a fossil (rock)
- measure the relative amounts (decay) of radioactive materials (parent) and their daughter products
- the radioactive isotopes (parents) spontaneously decay or break down over time to form stable daughter products
15
Q
relative vs absolute dating
A
relative age provides a comparative age whereas absolute age provides a more precise numerical age
16
Q
half-life
A
half life → the time taken for half of the original radioactive isotope to decay
17
Q
carbon dating
A
- carbon 14 will decay into nitrogen 14 (half-life of 5700 years)
- living things take in C14 when they eat living things stop taking in C14 when they die
- by comparing the amount of C14 and N14, the time since death can be determined
- limitation: can’t be used to date fossils older than around 50000 - 60000 years, there are very small amounts of carbon 14 left in the organic matter
18
Q
speciation
A
the formation of a new species
19
Q
process of speciation
A
- variation of characteristics is present in the population
- breeding population becomes isolated
- different selective pressures applied to isolated populations, random genetic drift, mutations
- b/c of natural selection, some characteristics are favoured over others
- those best suited to the environment survive
- survivors reproduce and pass on favourable genes + traits to offspring
- frequency of genes for new traits increases
- overtime, differences and mutations accumulate resulting in speciation
20
Q
definition of species
A
organisms that can breed and produce fertile and viable offspring
21
Q
allopatric speciation
A
- Initially a population (or populations) of the same species becomes isolated by a geographical barrier.
- Over time the isolated population(s) is exposed to different selective pressures and accumulates
- sufficient differences to the original population so that it forms a new species.
22
Q
galapagos finches
A
- 13 volcanic islands w/ a variety of habitats - arid regions and mountainous regions
- after finches had arrived on an island they would become geographically isolated
- differing environmental selection pressures on each of the islands based on food availability (main environmental pressure)
- caused change in beak shape bc of diff food source
- no gene flow
23
Q
sympatric speciation
A
- members of a populations living in the same area diverge to become 2 species
- no geographical barrier - both species continue to inhabit the same geographic region
- non-geographical barrier isolates populations from each other (active day/night) - some gene flow
- isolated populations are subject to different selection pressures → different phenotypes are favoured
- over generations, genetic divergence occurs
- responds to diff environmental pressures → different phenotypes and isolated populations change
- when the population come together again - can no longer interbreed - two separate species (2 distinct gene pools and different species)
24
Q
lord howe island palms
A
- there was variation in the lord howe island population
- shift in nutrient content in the soils which caused a shift in flowering times
- those that flowered at the same time would interbreed
- over time there was accumulation in the differences and mutations in the palms
- speciation occurs and the two species can no longer interbreed
25
Q
why is sympatric speciation rare?
A
- gene flow can still occur in sympatric speciation
- genetic drift has less of an impact
- less likely to be isolated as it requires reproductive isolation
- natural selection would need to be strong to favour specific traits that then lead to a divergence and a new species evolving
26
Q
what is a common ancestor
A
- is a species that existed earlier in the fossil record
- subsequently evolved into two or more different species
- an ancestor shared by later species: one from which two or more species evolved
27
Q
pre-zygotic/post zygotic isolation
A
- pre-zygotic: barriers that prevent an organism from finding and securing a mate
- post-zygotic: barriers that prevent fertile offspring from developing after mating
28
Q
relatedness
A
species that are more closely related are those that have most recently shared a common ancestor
29
Q
what is structural morphology
A
- the process of comparing similarities in body structures to infer relatedness
- fossil record
30
Q
structural morphology - homologous structures
A
- homologous structures are those structures that have been derived from a common ancestor
- would show similarities in structure
- even though they may have different functions
- evolution commonly occurs by modification of pre-existing structures - not by the production of TOTALLY new structures
- eg. mammalian forelimbs
31
Q
structural morphology - vestigial structure
A
- structures that are non-functional remnants of structures that were functional in ancestral species
- eg. tailbone in humans
32
Q
what is molecular homology
A
involves comparing the similarities in DNA and protein sequences to infer relatedness
33
Q
amino acids for molecular homology
A
- species that are more closely related are expected to have fewer differences in the amino acid sequences of their corresponding proteins than species that are more distantly related
34
Q
challenges with amino acid sequencing
A
- multiple triplets can code for a particular amino acid
- genetic code is redundant
- some mutations (silent mutations) aren’t visible in amino acid sequencing
- also sometimes two mutations that occur in the same codon will only cause one amino acid change.
