homologous & analogous structures (& evidence for evolution)

what’s sequence data

the ordered linear arrangement of molecules that carry genetic or functional info, such as DNA or protein

why does sequence data provide important evidence of common ancestry

since all living organisms hv the same nucleotide bases & amino acids, finding common sequence data in all organisms can provide proof that they originated from a common ancestor??

what is molecular phylogeny?

it is one method that can be used to prove common origin of life

is a comparative analysis of the base sequences in DNA, RNA & the amino acids in proteins, to infer evolutionary history

• basically sees DNA, RNA, & aa’s in protein to determine if the organism evolved from a common ancestor? - ask how exactly 

what else can molecular phylogeny be used for?

it can be used to determine how closely two species are related to each other at a molecular level

• more similarity in genes & proteins = more closely related species (and the more recently they split from a common ancestor?)

• alternatively, the more DNA or protein differences there are = the more distantly related they are (their common ancestor lived a long time ago)

  • this is cuz as time goes by, various mutations occur. these mutations accumulate & can result in 2 different species, even tho they hv a common ancestor

since mutations lead to differences in DNA & can accumulate over time, what does this mean for the amount of differences between DNA sequences (or base sequences of genes) ?

the amount of differences between the DNA sequences, will increase over time

• this forms the basis of the molecular clock

• accumulation of mutations also results in 2 (completely?) different species, even tho they hv a common ancestor

what is the molecular clock

it’s a technique that utilizes the mutation rate of biomolecules, to determine the time since two species shared a common ancestor

• ex: species that hv few differences in their genomes (& amino acids) would’ve recently split from each other

what is selective breeding/artificial selection

is when humans select individuals from a species to breed together, based on desirable characteristics

these chosen organisms will then be the parents to produce the next generation 

what happens to other organisms as this continues?

as humans consistently select organisms with desirable/favourable traits, there will be a removal of organisms with less favourable traits, resulting in a rapid genetic change in population

• selective breeding/artificial selection has to occur over a long period of time before a new variety in breed is produced

• can also selectively breed crops in order to increase disease resistance & yield

what does this process also lead to?

leads to evolution

• selective breeding/artificial selection is changing the genetic make-up of a population, leading to evolution 

what are homologous structures?

hv the same basic structure but hv different functions

• ex: pentadactyl limbs in vertebrates

what do homologous structures indicate?

indicates divergent evolution & common ancestry 

what’s divergent evolution

a pattern of evolution where organisms originating from same ancestral species, adapt to different environmental conditions according to pressures of natural selection 

what can divergent evolution lead to?

speciation

what’re analogous structures?

body parts that hv same/similar function in different groups of organisms, but hv different structures 

• ex: wings in birds & butterflies

indicates organisms evolved from different ancestors

is a result of convergent evolution

whats convergent evolution

pattern of evolution where distantly related organisms develop similar characteristics, in response to similarities in their environment

or - the similar selection pressures in their environments resulted in similar uses of different structures