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
