Evolution 🐒 Flashcards
(18 cards)
Define phylogeny:
Evolutionary relationships between organisms
Reveals which particular group an organism is related to.
What are phylogenetic trees?
Diagram used to represent evolutionary relationships between organisms.
Branched diagrams –> show different species evolved from common ancestor.
Produced by looking at similarities + differences in species’ physical characteristics + genetic makeup
Evidence gained from fossils.
State the advantages of phylogenetic classification:
Done without reference to Linnaean classification.
~> Produces continuous tree whereas classification requires discrete taxonomical groups. –> not forced to put species in a group it doesn’t fit from.
Linnaean system implies different groups in same rank = equivalent (some species lived for longer/different diversity)
Define evolution:
Theory describing ways in which organisms evolve/change over many years as a result of natural selection.
Best suited in environment = survive + reproduce –> pass on to offspring.
Over time = more advantageous phenotype for environment.
How did Darwin contribute to evolution?
Studies Finches in Galapagos Islands.
Different islands = different finches (beak+ claw size)
Concluded beak changed to be more suited to food present on island –> survive longer.
State the findings of Wallace:
What are the evidence for evolution?
Palaeontology
Comparative anatomy
Comparative biochemistry
What is palaeontology?
Study of fossils/fossil records.
Fossils –> plant/animals remains preserved in rock.
sediment deposited –> forms layers (different layers = different geological eras)
Sequence of oldest -> youngest showing how organism changes over time
What are the evidence provided by fossil records?
Fossils of simplest organisms (bacteria + simple algae) = found in oldest rocks –> fossils of more complex organisms (vertebrates) = more recent rocks
Sequence which organisms are found = matches ecological links to each other
Show how closely related organisms have evolved from same common ancestor.
Fossils allow relationship between extinct/living organisms to be investigated
State the issues of the fossil record:
Incomplete
Soft-bodied organisms decompose quickly before the chance to fossilise.
Conditions needed for fossils to forms = not often present.
Many fossils destroyed by earths movement (🌋)
Define comparative anatomy:
Study of similarities/differences in anatomy of different living species.
Used if fossil record incomplete
What is homologous structures?
Structure appears different (perform diff functions) but has same underlying structure
e.g: basic structure of all vertebrates similar
–> evolved from same common ancestor = same structure
What does homologous structures provide evidence for?
Divergent evolution
~> how different species evolved with different set if adaptive features.
Occurs when closely related species adapt to new habitat (migration/habitat loss)
Define comparative biochemistry:
Study of similarities/differences in proteins + other molecules that control life processes.
Some molecules = highly conserved
Slight changes = help identify evolutionary links
e.g: cytochrome c + rRNA
How are two species compared using comparative biochem?
Look at order of DNA bases –> order of AA in proteins
Number of differences plotted against the rate molecule undergoes neutral base pair substitutions
Closely related = more similar DNA
rRNA = slow rate of substitution .: more commonly used
What does the hypothesis of neutral evolution state?
Most variability in structure if a molecule does not affect its function.
Due to most variability occurs outside molecules functional region.
No effect on function = accumulation not affected by natural selection.
What is the mechanism for natural selection?
Random mutation causes organisms to have different characteristics
–> Exposed to selection pressures
Advantageous characteristics = organism more likely to survive + reproduce
Pass on alleles to offspring over generations
Define selection pressure:
A factor which affects organism’s chance of survival/ability to reproduce
