Evidence for evolution Flashcards
(50 cards)
1
Q
evolution
A
is defined as the change in the genetic composition of a population during successive generations, which may result in the development of new species
2
Q
microevolution
A
is defined as the small-scale variation of allele frequencies within a species of population, in which the descendant is of the same taxonomic group as the ancestor
- in simple terms this means the small changes in gene frequency within a population
3
Q
macroevolution
A
is defined as the variation of allele frequencies at or above the level of species over geological time, resulting in the divergence of taxonomic groups, in which the descendant is in a different taxonomic group to the ancestor
- this means big changes over long periods of time, causing speciation
4
Q
evidence for evolution comes from many different areas of biology:
A
- anatomy: species may share similar physical features because the feature was present in a common ancestor (homologous structures)
- comparative genomics: DNA and the genetic code reflect the shared ancestry of life. DNA comparisons can show how related species are
- biogeography: the global distribution of organisms and the unique features of island species reflect evolution and geological change
- fossils: fossils document the existences of non-extinct past species that are related to present day species
- direct observations: we can directly observe small-scale evolution in organisms with short lifecycles (e.g. pesticide-resistant insects)
5
Q
geological time
A
- evolution has occurred over very vast stretches of time
- geological time can be expressed in millions of years ago (mya)
- life on earth existed for 3.5 billion years
Eon -> Era -> Period -> Epoch
6
Q
continental drift
A
- over time, the tectonic plates have moved significantly
- the fossil record can attest to this, and the current biogeography is explained by continental drift
7
Q
biogeography
A
- the study of the distribution of organisms and ecosystems across the world and through geological time
- the geographical distribution of species provides evidence that now isolated locations were once close
- the differences between species in different locations can give an indication of how much time has passed since they were co-located
8
Q
evolution and continental drift
A
- biogeography provides evidence for evolution
- for instance, most of the mammal species in Australia are marsupials (carry young in a pouch), while most mammal species elsewhere in the world are placental (nourish young through a placenta)
- Australia’s marsupial species are very diverse and fill a wide range of ecological roles
- because Australia was isolated by water for millions of years, these species were able to evolve without competition from (or exchange with) mammal species elsewhere in the world
9
Q
fossils
A
- fossils are the trace of a previously living organism
- for example, hard parts such as teeth, bones and shells but also include impressions left after soft tissue has decayed, or footprints, leaves, burrows or preserves faeces (coprolites)
- different types of fossils can tell us how organisms looked and moved, what they ate, how they reproduced and how they lived
10
Q
types of fossils
A
- moulds - imprint left by organisms with rock around it
- casts - imprint has been filled with rock
- body fossils - trapped in a substance or skeleton/hard body structures
- trace fossils - indirect evidence like footprints, burrows of faeces
11
Q
fossilisation
A
- fossilisation is a rare process and very few organisms are preserved in the fossil record
- fossilisation one absence of oxygen
- in some situations, the hard parts of organisms (natural bone or shell material) are replaced with minerals. This is mineralisation and makes fossilisation more likely
- organisms can be covered with sediment such as silt or sand. This can protect the remains from scavengers and slow the decay long enough for fossilisation to occur
12
Q
fossilisation requires:
A
- rapid burial of the material (this will ensure conditions are not suitable for the activity of decay organisms)
- presence of hard body parts
- long period of stability - the organism needs to be left undisturbed
- alkaline soil so that the minerals in the bones are not dissolved
13
Q
relative dating
A
used to determine the age of a rock, fossil contained in the rock, relative to other rocks or fossils found nearby
- strata are deposited in a time sequence, with the oldest on the bottom and the youngest on the top (principle of superposition)
- Palaeontologists can assign relative ages to fossils based on the strata in which they are found
14
Q
absolute dating
A
assigns a numerical age in years to a fossil or rock
- three main types: radiometric dating, electron spin resonance and luminescence
- most common methods of absolute dating is radioactive dating, which uses the known rates of decay of naturally occuring radioactive isotopes present in a rock or fossil
15
Q
law of fossil succession
A
- fossils can be dated by determining the age of the rock layer (strata) in which the fossil is found
- sedimentary rock layers develop in a chronological order, such that lower layers are older and newer strata form on top. This is called the principle of superposition
- each strata represents a variable length of time that is classified according to a geological time scale (eons, eras, periods)
- different kinds of organisms are found in rocks of particular ages in a consistent order, indicating a sequence of development
– prokaryotes appear in the fossil record before eukaryotes
– ferns appear in the fossil record before flowering plants
– invertebrates appear in the fossil record before vertebrate species
16
Q
the principle of superposition
A
the principle of superposition indicates that the oldest rock layer is found at the bottom of the rock, with each consecutive layer above being relatively younger
17
Q
fossil records
A
evidence for early forms of life comes from fossils
- by studying fossils, scientists can learn how much (or how little) organisms have changed as life developed on Earth
- there are gaps in the fossil record because many early forms of life were soft-bodies, which means that they have left traces behind. What traces there were may have been destroyed of geological activity. This is why scientists cannot be certain about how life began
- fossils provide a snap shot of the past and allow us to study how much or how little organisms have changed as life developed on Earth
18
Q
transitional fossils
A
- show characteristics of both ancestral and descendant groups, showing a mid point in the evolutionary process
- transitional fossils demonstrate the intermediary forms that occurs over the evolutionary pathway taken by a single genus
- they establish the links between species by exhibiting traits common to both an ancestor and its predicted descendants
- an example of a transitional fossil is archaeopteryx, which links the evolutionary patterns are emerging and old assumptions are challenged
19
Q
the fossil record is incomplete
A
- the process of fossilisation requires very specific, and rare, conditions. The remains of the vast majority of long-extinct animals may never be found
- consequently, the fossil record is incomplete and biased toward organisms that lend themselves more easily to the fossilisation process
20
Q
comparative anatomy and embryology
A
comparative anatomy is the study of the similarities and differences in structure between organisms. Structural features are also called morphological features
- used to establish evolutionary relationships on the basis of structural similarities and differences, including the comparative study of embryos (embryology)
- longer they look the same - the closer related they are
21
Q
homologous structures
A
anatomical structures that are common to more than one species and were inherited from a common ancestor, but have different functions
- show the same structural plan but perform different functions due to the different species living in different environments with different selective pressures (conditions)
22
Q
pentadactyl limb
A
5 limbs, same pattern of bones, different size and shape - function
23
Q
divergent evolution
A
- is a pattern of evolution in which differences between groups of organisms accumulate to a critical point that leads to speciation, the development of a new species
- this pattern is usually the result of the dispersal of a single species to different environments, that is, groups from the same species become isolated from one another, stopping gene flow
- the sub-populations are subjected that can perform functions specific to surviving their unique environment
- homologous structures indicate divergent evolution, because new species will have the same fundamental structural plan, but the structures may be used in different ways
24
Q
adaptive radiation - a type of divergent evolution
A
- the evolution of an ancestral species, which was adapted to a particular way of life, into many different species, each adapted to a a different habitat
- adaptive radiation involves rapid speciation, and is likely to occur after an extinction event that creates many vacant ecological niches or colonisation of a new area
- example: darwins finches in the galapagos islands - evolved beak shapes - according to what they ate
25
analogous structures
analogous structures are features of organisms that have the same function but not the same basic structure
26
convergent evolution
- a pattern that occurs when unrelated organisms evolve similar adaptations in response to their environment
- often results as analogous structures: adaptations of very different types of structures are genetically relatively different, but their functionality is very similar
is where species that aren't closely related have evolved similiar traits due to similar selection pressures within their environment. if we were to rely on morphological characteristics to determine the degree of relatedness between these species, we would likely think they were more closely related than they truly were
27
vestigial homologous structures
- homologous structures from a common descent can eventually cease to have any functional use for an organism
- the structure may not necessarily impede a particular adaptation of an organism, but at the same time the structure no longer serves a 'useful' purpose
- vestigial structures can take a variety of forms, including bones, soft tissues, organs, cells, or molecules
- vestigial organs are evident for evolution, because it is hypothesised that they were once present and functional in their ancestors
- changes in the environment have rendered these organs redundant, so over time they have lost their functionality
- they demonstrate the evolutionary divergence of a species from a past behaviour or activity
28
genomics
is the study of the whole set of genes of a species and the interactions of the genes within a genome. The genomes of many species have been fully sequenced. Complete genomes if many species have been fully sequenced. Complete genomes are now available for humans, chimpanzees, koalas and bacteria, among others
29
relatedness
is a measure of evolutionary distance.
The relatedness of groups of organisms is reflected in the similarity of their DNA sequences.
Two species are more related if they have a more recent common ancestor and less related if they have less recent ancestor
30
comparative genomics
is a field of biological research in which researchers use a variety of tools to compare the genome sequences of different species. The more similar in sequence the genes and genomes of two species are, the more closely related those species are
31
biological classification
is the categorisation of living organisms into similar groups according to certain criteria.
- involves the organisation of living organisms into similar groups according to certain criteria. These groupings used to rely on morphological characteristics: organisms that had similar features were assumed to be closely related. Unfortunately, using only morphological characteristics to infer species relatedness got tricky in cases of convergent evolution
- Its a method of organising the millions of species on Earth in a meaningful way that helps scientists to understand certain evolutionary relationships between them
- it involves describing and naming different organisms, then organising these species into a group with other, closely related species
- grouping species makes it easier to see information about them and provides a system in which species can be classified in a predictable way
32
species definition
a group of similar organisms that are capable of interbreeding to produce viable, fertile offspring
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how is biological classification helpful
- it helps determine how closely related different organisms are, and when they last shared a common ancestor
34
DNA hybridisation and - species relatedness
- provides a way to compare genomes of different species by measuring the degree of genetic similarity between DNA sequences
- the more similar the DNA sequences of two species are the more closely related the two species are
35
DNA hybridisation steps
1. DNA from the two species to be compared is extracted, purified and cut into short fragments
2. the DNA of one species is mixed with the DNA of another
3. the mixture is incubated to allow DNA strands to dissociate and reanneal, forming hybrid double stranded DNA
4. the hybridised sequences that are highly similar will bind more firmly
5. a measure of the heat energy required to separate the hybrid strands provides a measure of DNA relatedness
- the lower the temperature that is required to split the hybrid strands of DNA compared to the DNA of the original species the less similar the species are
36
DNA sequencing
- was a time-consuming and expensive process right up until the 1970's, when scientist Frederick Sanger developed faster, more efficient techniques. This was called the Sanger sequencing process and gave a platform for other, more refined techniques to also be developed
- now, modern DNA sequencing allows for a direct comparison of the exact sequenced of the four bases that make up an organisms DNA. In contrast, hybridisation can only estimate the differences between the DNA of different species
- this means that scientists can determine the exact number of similarities or differences between the DNA sequence of two different species. More closely related species will show more similarities in their base sequences
37
Sanger definition - DNA sequencing
the discovery of the Sanger sequencing process was enough to earn Sanger himself a noble prize in 1980. This technique is still used today, but other ones have been developed that take even less time and cost less as well. These include pyrosequencing and nanopore sequencing
38
DNA sequencing - species relatedness
- if two organisms share the same DNA sequences, then we can say that they are the same species. If they had only a small number of differences in the order of the bases, then we can say they are closely related
- if the two organisms had a large number of differences in the order of the bases in the DNA sequences, then we can say they are distantly related. Their last common ancestor would have existed tens, if not hundreds, of millions of years ago
39
Amino acid sequencing
- amino acid sequences form larger molecules called proteins
- as species accumulate mutations the sequence of the amino acids that form proteins will change
- as such we can isolate a particular protein (often called a ubiquitous protein) that we know is found in multiple different species. We can then compare the amino acid sequence for each species that results ultimately in the formation of the same protein
- if two species share a recent common ancestor, then they will be closely related and the respective amino acid sequence for the chosen protein will be very similar
40
Cytochrome C
- is an example of an ubiquitous protein
- Human Cytochrome C has 104 amino acids
- 27 of the amino acids in Cytochrome C are found in every molecule sequenced, from bacteria to humans
- performs essential step in cellular energy production
- has changes little over millions of years of evolution
- strong evidence that the genes for Cytochrome C production originated from a primitive microbe ancestor, more than 2000 million years ago
- Cytochrome C of chimpanzees, gorillas and humans is identical
41
Bioinformatics
- is the digital storage, retrieval, organisation and analysis of an enormous volume of biological data
- Bioinformatics has dramatically increased the size, accuracy and scope of data sets, such as those needed for comparative genomics
- bioinformatics has provided significant advances in our knowledge of the entire genomes of organisms, and in turn this has revealed yet more evidence of evolution
42
Phylogenetic trees
- evolutionary relationships between groups can be represented using phylogenetic trees
- these diagrams show how organisms are related to each other, but the tree is a hypothesis, not a certain fact
- a phylogenetic tree can be built using:
-- physical information, such as body shape, bone structure or behaviour
-- molecular information, such as genetic sequences
- essentially the species that are considered more closely related (they might share key morphological characteristics and have similar sequences of amino acids of DNA) will be grouped into clades
43
parts of a phylogenetic tree
- root
- node
- outgroup
- clade
- taxon
44
root
initial ancestor
45
node
hypothetical common ancestor where branching occurs
46
outgroup
most distantly related species
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clade
a group of organisms that include a common ancestor and all its descendants
48
taxon
a group of organisms (can refer to any rank; species, genus, family, etc)
49
phylogenetic trees construction
remember, when looking at a phylogenetic tree, we are most interested in the positions of the nodes and grouping of branches as this represents the evolution of taxa. While all four different tree types (horizontal, vertical, diagonal and square) look different, it is important to realise that one set of data represented by each different type of trees will always depict the same evolutionary relationships
50
phylogeny
explains similarities and differences between organisms
establishes relationships between groups
