Topic 5 Flashcards
(41 cards)
1
Q
Define evolution [1]
A
cumulative changes in the allele frequency of a population’s gene pool over successive generations
2
Q
define fossil
A
preserve remains or traces of an organism from the remote past
3
Q
how fossils provide evidence for evolution
A
- preserved remains provide direct evidence for evolution, incl/ teeth, bones, etc.
- traces provide indirect evidence for evol and incl/ footprints, tooth marks, etc.
4
Q
define the fossil record
A
the totality of all fossil, both discovered and undiscovered. it shows that over time, changes have occurred in the living organisms’ features
5
Q
fossil dating
A
- the fossil can be dated by determining the age of the strata/rock layer it was found in
- fossils develop in sedimentary rocks -> lower layers form before upper layers
- various organisms found in a particular order in rocks of different ages:
- prokaryotes before eukaryotes
- ferns before flowering plants
- invertebrates before vertebrates
6
Q
Law of fossil succession
A
chronological sequence of complexity by which characteristics seem to develop. the law of succession indicates that new organisms formed from changes to older organisms
7
Q
limitations of the fossil record
A
- record is incomplete –> don’t have all the fossils to clearly see evolutionary changes
- fossils require specific conditions to form -> not all organisms fossilise
- only hard parts of organisms preserved -> only fragments of organism fossilised
- with limited fossil data, difficult to discern evol. pathways -> missing links
8
Q
transitional fossils
A
- intermediary forms that occur over the evolutionary pathway of a single genus
- displays characteristics shared by ancestor and descendant
- eg:- archaeopteryx -> links evolution of dinosaurs to birds
9
Q
example of how fossils used as evolutionary evidence
A
australopithecus skeletons compared to homo sapiens skeleton to see evolutionary changes
10
Q
Selective breeding
A
a form of artificial selection by which man breeds organisms with desired traits, increasing the frequency of the trait in population
- provides evidence for evolution as offspring show large amount of variation in a short span of time
11
Q
Selective breeding examples
A
- used to produce new types of crops. Brassica genus selectively bred to produce broccoli (modified flower buds), kale (modified leaves)
- horse: different types of horses bred for different functions. Race horse -> speed, hence bred to be leaner, lighter taller. draft horses for power and endurance -> sturdier, heavier
- dogs: dogs with different qualities bred for various functions
- cows: selectively bred for improved milk production. increased breeding of cow w a mutation that causes it to have increased muscle mass (belgian blue)
12
Q
Homologous structures
A
- structures that are similar in basic structure, despite being used in different ways
- evidence of adaptive radiation, where new species rapidly diversify from the ancestral source, which each species utilised a specific, unoccupied niche
- the more similar the HSs are, the closer organisms are likely to be
Eg: - pentadactyl limb
- the 5 digit limb with a similar arrangement of bones
- in humans -> used for gripping and holding, in birds -> used for flying, in horse hooves -> galloping, whale/dolphin fins -> swimming
13
Q
speciation process
A
- there is variation in a population and it often follows a continuous normal distribution curve
- if 2 populations are geographically separated, they begin to adapt to their different environments, and diverge from one another
- with increased time, separated populations faced increased divergence, and lowered genetic compatibility. if the populations diverge to the extent where they cannot interbreed when put in same environment -> separate species
14
Q
speciation definition
A
the evolutionary process by which 2 related populations diverge into separate species
15
Q
5 processes of natural selection
A
- variation: variation exists between members of a population -> can be inherited
- competition: lower resources for pop -> struggle for survival
- selection: differential reproduction occurs due to env selection pressures
- adaptations: organisms with beneficial traits more likely to pass on to offspring
- evolution: over time, there is change in allele freq. in gene pool
16
Q
Explain how natural selection can lead to speciation
A
- variation is required for natural selection
- as a result of mutation/sexual reproduction
- there are more organisms than environment can support/competition
- adaptations make organisms more suited to their environment
- survival of better adapted individuals
- organisms with beneficial traits are more likely to survive and pass on traits to offspring
- speciation is the formation of a new species from one population
- reproductive isolation of separated populations
- geographical isolation can cause it
- temporal/behavioural isolation can cause it
- natural selection within 2 separated populations causes them to diverge from one another -> speciation
- disruptive selective often separates 2 populations
- changes in gene pools of separated populations
- 2 populations cannot interbreed to produce fertile, viable offspring
17
Q
describe the changes that occur in gene pools during speciation [5]
A
- gene pool is all the genes/alleles in an interbreeding population
- the gene pools splits when the popualtion splits
- due to reproductive isolation of groups within species
- due to behvioural/temporal isolation between species
- natural selection causes gene pools of the 2 groups to gradually diverge
- diverge of gene pools
- allele frequencies change
- different random mutations occur in each population -> more divergence
- until the populations cannot successfully interbreed
18
Q
Outline evidence for evolution provided by selective breeding [3]
A
- crop/plants/livestock animals produced by selective breeding
- eg- new varieties of plants like broccoli and kale produced by growing modified varieties of the Brassica genus. Cows with increased milk production/ Belgian blues with more muscle mass bred for meat and milk
- evidence as show a rapid change in characteristics over s short period of time
- changes due to selective breeding show that natural selection can cause changes/evolution in species
19
Q
How genetic variation between individuals in a species can be generated [7]
A
- mutations
- base substitution
- can cause various alleles for a particular gene
- radiation/mutagens increases chances of mutations
- meiosis
- sexual reproduction -> random fertilisation and fusion of 2 gametes
- independent assortment -> due to random orientation, 2^n ways in which the chromosomes can be sorted
- crossing over of genes in P1 -> creates recombinants, increases variation
- in reproductively isolation populations nat selection may differ
- in small/isolated populations gene pools change
- disruptive selection can cause different varieties to diverge
20
Q
competition
A
- malthusian dilemma -> population grows geometrically while food grows arithmetically
- stable population will outgrow its food base
- more offspring than the environment can support -> environmental resistance
- struggle for survival, increased mortality rate
21
Q
5 types of adaptations
A
- structural: physical differences in biological structure (eg length of giraffe neck)
- biochemical: differences in the molecular composition of cells and enzyme functions (eg blood groups)
- behavioural: differences in organisms patterns of activity (eg possums faking death when threatened)
- physiological: variations in detection and response by vital organs (eg colour perception)
- developmental: varibale changes occurring across the organism’s lifespan (eg ageing patterns)
since biological adaptations have a genetic basis -> can be inherited
22
Q
Adaptive radiation
A
- The rapid evolutionary diversification of a single ancestral line. when organisms of a single species occupy various environmental niches and develop morphological characteristics in response to various environmental selection pressures. eg :- finches on galapagos islands have different beak shapes -> different foods
23
Q
Daphne Major birds
A
Darwin’s finches on the Galapagos islands. they have a variety of beak sizes and shapes adapted to their varied diets -> larger beaks for those which fed on larger seeds with tougher casings
one year there was drought -> increased seeds with tougher casings. more finches had larger beaks -> finches with larger beaks more likely to reproduce that year -> natural selection
24
Q
Benefits of binomial naming system
A
- easy to identify and compare organisms based on recognisable characteristics
- allows evolutionary links between organisms to be recognised -> how closely related organisms are
- easy to collect, sort and store info about organisms
- a globally recognised scheme for identifying and naming organisms
25
What are the domains of life
- Eubacteria: prokaryotic cells, lack compartmentalisation and membrane bound nucleus -> consist of common pathogenic forms
- Archaea: prokaryotic cells that lack nucleus and are extremophiles -> eg thermophilic bacteria
- Eukarya: eukaryotic organisms containing a membrane bound nucleus
26
define taxonomy
the classification of organisms into groups based on shared characteristics. they are grouped according to series of hierarchal taxa
- the more taxa organisms share the more closely related they are (KPCOFGS)
27
Describe artificial classification
- organisms grouped together based on the similarity of characteristics -> analogous traits
- doesn't consider whether they have evolved from same ancestors -> brings together dissimilar species
- A: easy schemes to develop, unlikely to change
28
Describe natural classification
- when organisms are grouped together based off of common ancestry -> identifying similarities then identifying shared characteristics
- more often used because it allows for evolutionary links to be seen and allows for prediction of characteristics shared by species
- DA: Highly mutable -> change as new info discovered
29
phylogenetic classification
- newer type
- organisms with greater amount of homology in their DNA/AA sequences for common genes/proteins -> closer together
30
Example of changes in natural classification
- species originally classified as figworts were then classified as a different genera based on new evidence indicating different ancestry
- chimpanzees and gorillas were added to the Homininae sub-family upon new evidence suggesting shared ancestry with humans than other great apes
31
what is a dichotomous key
- a graph that keeps dividing into 2 categories, until the organisms doesn't share totality of selected characteristics anymore -> it has been identified
- with each division, more specifc info about organism is revealed
- types of featured used: biological processes or physical characteristics that aren't subject to change
32
Define cladistics
the practice of classifying species into groups called clades
33
Define clade
An ancestral organism and ALL its evolutionary descendants
34
What are cladograms
- tree diagram
- each branch point/node represents a speciation event -> divergent evolution took place -> 2 distinct species formed from a common ancestor
- allows for the likely evolutionary history of a clade to be mapped
- fewer nodes between 2 groups -> more similar they are
according to cladograms, chimpanzees, gorillas, humans, orang-utans and gibbons are part of the Hominoid clade. hominoid clade is part of a larger clade -> anthropoids
35
features of cladograms
- root: the original ancestor common to all the organisms in the clade
- node: the hypothetical ancestor that speciated to give rise to 2 or more daughter taxa
- outgroup: the species that is the most distantly related. functions as the point of comparison and reference group
- clade: a common ancestor and ALL of its descendants
36
Ways to create cladogram
Structural features:
- use structural organism features that aren't subject to environmental pressure -> eg hair, amniotic egg, number of limbs, etc.
- sequentially order organisms according to shared characteristics
Molecular evidence:
- use genbank or other software to find DNA or AA seq for certain proteins/genes shared by all org -> eg cytochrome c
- run software to see which organisms aa seq has the most simialrity
37
How molecular evidence works + types of evidence used for different purposes
- mutations in the gene/dna/aa sequences accumulate over years
- aa can be compared due to the universal genetic code, dna can be compared for comparable base sequences
- more similar the sequences are -> lesser time has passed since the species diverged
- Non coding DNA: highest mutation rate-> best means of comparison -> mutations will occur more readily
- coding dna: slightly lower mutation rate -> mutations would result in altered proteins structures
- AA seq: lowest mutation rate -> degenerate code. used to compare organisms that are very distantly related
38
Molecular clock concept + limitations
- some proteins/gene sequences mutate at a fairly constant rate. if the rate is reliable -> one can estimate how long ago divergence took place
limitations:
- the rate of mutation may vary between different organisms
- later mutations may 'undo' or reverse earlier mutations -> lowers the accuracy
- different genes/proteins may mutate at different rates
39
Convergent evolution
the independent evolution of similar structural features in species with distinct lineages
- organisms may occupy same habitat -> subjected to similar selection pressures
- features that benefit survival in the environment differentially selected
40
Analogous vs homologous traits
Analogous:
- traits that are superficially structurally similar but derived through separate evolutionary pathways
- due to convergent evolution
- used in artificial classification -> brings together dissimilar species
Homologous:
- traits that are similar as they have been derived from a common ancestor but have developed to be used in different functions
- pentadactyl limb
- due to divergent evolution/adaptive radiation
- natural classification is based on homologous -> predictive values/matches evolutionary history
41
Reclassification of figworts
- figworts were the 8th largest family of angiosperms
- many figwort species were too dissimilar
- genetic analysis was conducted of chloroplast gene
- figworts split into 5 different clades
