Chapter 8: Evidence for the Theory of Evolution Flashcards
define fossil
remains, impressions, or traces of life forms that have been preserved in material such as ice, sediment, or amber.
what is the fossil record
the total collection of fossils that have been discovered so far.
what is relative dating
involves arranging fossils in chronological order
does not give fossils a numerical age
qualitative method of dating
how does relative dating work
using the comparison of the position of rock strata that contain fossils to determine the comparative time scale of their occurrence. works on the law of superposition: each rock layer is older than the own above it.
it also works on index fossils, fossils that existed for a limited period of time that can be used as guides to determine the relative age of rocks in which they are preserved.
what is absolute dating
provides a precise estimate of a fossil’s age
provides a fossils specific numerical age
quantitative method of dating
how does absolute dating work
it works using radiometric dating, where fossils’ ages are determined from the decay of radioisotopes. most common ones are carbon 14, and uranium lead.
how do fossils provide evidence for the theory of evolution
- fossils show a clear transition from simple forms to complex life forms
- fossils indicate that there has been a vast increase in biodiversity over time.
- fossils have allowed scientists to approximate the first appearance of life on earth
- transitional fossils show a clear transition from one species, or group, to another.
Explain how biologists know about the evolution of the forefeet in horses over the past 50 million years.
Biologists know about the evolution of the forefeet in horses due to collection and data from the fossil record. The preserved bones of the forefeet of horses discovered over time has contributed to our understanding of their evolution. These fossils have been compared and aged using dating technology of the bone or the surrounding rock.
‘Absolute dating is the preferred method used by scientists for the ageing of fossils.’
Evaluate this statement by comparing relative and absolute dating methods for the ageing of fossils.
Relative dating involves arranging fossils in chronological order. It is achieved by comparing the placement of fossils in various layers of rock. This means that relative dating does not give fossils a numerical age, so it can only be used to determine the sequential order in which fossils were formed.
Alternatively, absolute dating provides a precise estimate of a fossil’s age. This can be achieved through radiometric dating. Radiometric dating is the process of determining the age of rocks or fossils from the decay of their radioisotopes. Therefore, by comparing the proportion of radioisotope in the fossil or rock sample to the proportion that it exists in the environment, scientists can determine how much radioactive material has decayed and use the substance’s half life to get a fairly accurate date of when it began to decay.
Because absolute dating is quantitative, it is usually the preferred dating method used by scientists. However, relative dating can be quite inexpensive and is still a great tool for collectively placing specimens on a time scale continuum. Therefore, while absolute dating is the preferred method, relative dating is still a useful tool in paleontology.
moleculuar evidence for evolutuon
comparative genomics
protein sequencing
DNA sequencing
how does comparative genomics work?
all species use a genetic code of DNA or RNA to determine what they look like and how they function.
DNA sequencing
scientists have come to realise that species thought to be closely related to each other have similar genomes.
why is mitochondrial DNA used?
called mtDNA
any changes to mtDNA occur due to mutation only
we know the rate at which these mutations accumulate over time. this means we can sequence mtDNA and use it to date genetic events
can compare individuals mtDNAs to estimate when they had a common ancestor.
how does protein sequecning work
choose a common protein that exists in both species
Proteins are made of amino acids (AA)
amino acids are coded for by DNA
by looking at the particular AA sequences for a particular protein, we can find out the DNA that coded for the protein. similar AA sequences = similar DNA = closely related and vice versa.
Describe how DNA sequencing provides evidence for evolution.
Evolution is a biological process that describes how – by accumulating small genetic changes – species slowly adapt to their environment. Using DNA sequencing, biologists have been able to compare the genomes of species and therefore demonstrate changes within and between species over time. For example, by comparing the entire DNA sequence of humans and chimpanzees, scientists have been able to determine that the two species are genetically very similar, with a difference of only about 4%. This supports the theory that humans and chimpanzees diverged from a common ancestor, and therefore supports the theory of evolution.
Describe how biologists might compare organisms using biological molecules, besides DNA.
Protein sequencing involves using a type of protein from two different organisms to compare how similar these proteins are in different species. This should be done using a common protein, such as cytochrome C. Because proteins are coded for by DNA, knowing the amino acid sequence of cytochrome C in one species and comparing that to another species can provide an idea on the similarity of their DNA. Organisms with similar amino acid sequences for their cytochrome C protein are likely to have similar DNA and be closely related. Those with different amino acid sequences are likely to have different DNA, and so be less closely related. Therefore, protein sequencing is a method that can be used to molecularly compare species without using DNA.
Compare protein sequencing and DNA sequencing. In your answer, provide TWO similarities
both used to determine similarities/differences between species
both compare DNA (amino acid sequences)
Compare protein sequencing and DNA sequencing. In your answer, provide TWO differences.
molecules used: proteins, DNA
DNA sequencing is more precise, and protein sequencing is less precise.
why does comparative embryology give evidence for evolution
the structural similarity of embryos suggests that different species are interrelated
this further suggests that they must have common genes, wihch came from a common ancestor
embryos of a species often have strcutres that arent in the adult form, this allows us to see similarities between spceis that look very different in the adult form.
Explain the purpose of comparative embryology.
Comparative embryology is the study of the embryological structure of different species, and involves assessing their similarity. This is used to determined the ‘relatedness’ of species and therefore their evolutionary relationships.
Discuss how the existence of convergent evolution poses a problem for comparative anatomists.
Comparative anatomy demonstrates how all species evolved from a common ancestor by identifying homologous structures that exist within a diverse array of species. For example, all mammals, including humans, whales, bats, horses, rhinos, and birds, all share the same arrangement of bones in their forelimb. However, the appearance or apparent structural similarity of organisms does not necessarily indicate relatedness. For example, dolphins and sharks are structurally similar organisms. However, these organisms possess very different DNA. In fact, genetic analysis tells us that sharks descended from a fish ancestor, but dolphins descended from a mammalian ancestor.
This can be accounted for by convergent evolution, which is when species will evolve to appear similar because they are influenced by the same selective pressures. In other words, they evolve independently, but ‘towards’ each other. Therefore, comparative anatomists should use comparative anatomy in conjunction with genetic information when assessing evolutionary similarity so that they do not confuse homologous structures with analogous structures.
Explain how comparative embryology can provide evidence for the theory of evolution.
Comparative embryology involves investigating the similarities and differences between the embryos of different organisms. The similarity of embryos at the early stages of development suggests that we all came from a common ancestor at some point. On a genetic level, because the development of embryos is driven by master genes, we can infer that all vertebrates have similar master genes that were inherited from a common ancestor. For example, when we examine vertebrate embryos, they all possess gill and tail-like structures at some point in development - even though they don’t all end up developing them in adult form. This suggests that all vertebrates share a common ancestor with a tail and gills.
Explain how comparative anatomy can provide evidence for the theory of evolution.
Comparative anatomy demonstrates how all species evolved from a common ancestor by identifying homologous structures that exist within a diverse array of species. For example, all mammals, including humans, whales, bats, horses, rhinos, and birds, all share the same arrangement of bones in their forelimb. These shared bone structures aren’t particularly efficient for carrying out all of these different functions, and therefore have not been developed specifically for each organism. Therefore, the sheer unlikelihood of the same structure being prevalent in all species suggests that these species evolved from a common ancestor.
Explain how differences in the amino acid sequence of a protein can provide evidence
of evolutionary relationships between organisms.
sequence of amino acids in a protein is determined by a DNA
sequence
the more similar the amino acids, the more similar the DNA sequence
organisms with similar DNA/amino acid sequences are closely related
because they diverged more recently
less time to accumulate mutations/differences
Describe how genetic drift affects the genetic composition of populations.
- changes allele frequencies
- changes are random or occur by chance
- (causes) loss of diversity/alleles from a population
- (causes) differences between populations
Explain how the larger horns in the males of this species could have evolved.
larger horns are not favoured by natural selection
females preferred the males with larger horns/males out-compete
other males to mate with females
males with larger horns were more likely to mate or breed
therefore males with larger horns left more offspring than males with
smaller horns or passed on allele/s for larger horns to offspring
therefore the frequency of allele/s for large horns increased over time
Explain how new species of dung beetle could evolve by allopatric speciation.
- a physical barrier divides population/geographical isolation
- prevents gene flow (between the different populations) or individuals
- (from the different populations) from interbreeding
environment/conditions/selection pressures on either side of barrier are different - population on either side of barrier become different due to natural selection
- may also become different due to mutation or genetic drift
- differences will increase/accumulate over time
- if individuals are no longer able to interbreed, new species or speciation
Explain how a phylogenetic tree can represent the evolutionary relationships &
different species.
- branching of the tree represents the relationships
- recent/descendent species are at the tips of branches
- shared/common ancestors are at base/trunk of the tree
- nodes/branching point represent a common ancestor
- branch length represents divergence time/similarities/differences
- closely related species will be grouped in same part of tree or unrelated species will be grouped in different parts of tree
- tree constructed from DNA/morphological/biochemical data (which
reflect relationships)
Habitat destruction has reduced the opportunity for gene flow between malleefowl
populations. Explain how gene flow affects the gene pool of a population.
gene flow is the exchange of genetic material/alleles between
populations
gene flow/migrants/immigrants can bring new alleles into the gene
pool/population
because they come from populations with different alleles
gene flow/migrants/immigrants can change allele frequencies in the
allele in the gene pool/population
because they come from populations with different allele frequencies
gene flow/migrants/immigrants reduce differences between the gene
pool of the source and recipient populations
Explain why populations with reduced genetic diversity face an increased risk of extinction.
Extinction occurs when a species fails to adapt to its environmental conditions or is
outcompeted, causing the entire species to cease to exist. Low genetic diversity within a
population means most individuals will have the same/similar genetics.
This means if a
selection pressure arises, there is a lower likelihood a beneficial variation will exist in the
gene pool of the population. As a result, the species will be unable to adapt to the
selection pressure and will most likelu become extinct.
Explain microevolutionary change through mutation.
Microevolution.refers.to.small.scale.variation.in.allele.frequencies.in the gene pool of. a species,
causing changes without creating. an entirely new species..This.can occur through mutation
whereby:
I. Random mutations are generated over time and result in new alleles in a population
2. Beneficial mutations will enhance survival and result in the allele becoming more common
in the population
3. The species will be changed without a new species being formed
discuss genetic drift in terms of defintion, chance and population size
Definition: When random events occur within a
population, like births and deaths,
leading to changes in allele frequency.
Chance: Random
Population Size: More common in small populations
discuss natural selection in terms of definition, chance, and population size
Definition: The process whereby organisms better
adapted to their environment tend to
survive and produce more offspring.
Chance: Not random
Population Size: Can occur in small or large populations
Describe the features of the theory of natural selection to explain how this may have occurred.
Due to genetic variation, some individuals in a population will have inherited traits that help them
survive and reproduce when certain selection pressures (changes in the environment which impact an organism’s chance of survival) arise, since the helpful traits are heritable, those with the trait are
more likely to survive and pass it on to offspring. This means the trait will become more common in the population and over time the population will become more adapted to its environment. In the case of the lung fish, if the environment remains relatively unchanged (i.e. no new predators or competitors, still a water-dwelling organism), there is no environmental selection pressure to select for any new mutations in morphology, so there is minimal change in the species.
how can molecular evidence be used for fucken idfk fuck this gay ass bs.
- TO SEPARATE DNA STRANDS BY LENGTH/SIZE (1 mark)
- STEPS:
o DNA samples and ladder (‘ruler’- standard set of molecule size markers [1/2]) added to wells (in agarose gel) (1)
o Electric current turned on- DNA molecules/fragments move towards the positive (cation) end (1) (DNA is negatively charged due to phosphate group) (1/2)
Smaller fragments move faster and end up further along the gel. (1/2)
o Visualise- fragments are photographed, they appear as bands. Fragments have been tagged with a dye in order to be seen. (1)
o Comparison of samples. (1/2)
what arfe vestigial tissues why can they be used for evidence
A structure that no longer provides a function or serves a useful purpose
May be skeletal, soft tissue, cellular or molecular
Usually rudimentary or atrophied
Evidence of a link to a common ancestor
eg
* Whale pelvic bones- bones formally a pelvis shows a link to chordates via a common ancestor.
* Human Appendix- may be a shrunken caecum, shows relatedness to other primate herbivores such as gorillas, orang-utans who retain large caecums.
what are homologous structures, why can they be used for ___________ evolutinol.
Comparative anatomy/homologous structures
Common physical structures shared by different organisms but having different functions
Evidence for divergent evolution (adaptive radiation), shows relatedness through a common ancestor.
Same basic structures have adapted to suit differing environments.
Examples:
* Pentadactyl limb
* Lizard skin
* Leaves
