B15 - Genetics and evolution Flashcards
Who developed the Theory of Evolution? Describe how:
-Charles Darwin
-went to Galapagos Islands and made many observations
-linked them to the developing knowledge of geology/fossils
-published in his book, On the Origin of Species (1859)
Describe what the Theory of Evolution proposes:
-organisms within a certain species show variation for a particular characteristic
-individuals with characteristics most suited to the environment are more likely to survive and breed successfully (natural selection)
-the characteristics that enabled these individuals to survive are passed on by alleles to the next generation
(VNP)
Why was there controversy surrounding Darwin’s work?
-challenged the religious idea that God made all the plants/animals on Earth
-insufficient evidence at the time, nothing to convince scientists
-the mechanism of inheritance and variation wasn’t known until 50 years later
What did Lamarck do?
Jean-Baptiste Lamarck proposed the idea that changes that occur within an organism’s lifetime can be inherited by their offspring
Why was Lamarck’s idea not accepted?
this type of inheritance can’t occur in most cases (eg if a person worked out a lot and became very muscular, they wouldn’t necessarily pass on a “muscular gene” to their offspring)
How was Wallace’s ideas relate to Darwin’s work?
Alfred Russel Wallace had independently proposed the theory of evolution by natural selection, and made joint writings with Darwin in 1858, which led to Darwin writing his own book in 1859
What did Wallace do, and what is he best known for?
-Alfred Russel Wallace gathered evidence for evolutionary theory
-he is best known for his work for warning colouration on animals, and the theory of speciation
Describe the general process of speciation:
Can be applied to any context
-variation in population due to sexual reproduction + mutations
-isolation of some members of the species (name the barrier, eg continental drift)
-members with best characteristics in each isolated group are more likely to survive and reproduce, and pass down different favourable alleles (those that are best suited to the different environments)
-isolated groups evolve differently depending on their environment due to natural selection
-over time, they become so different and eventually can’t breed between groups to produce fertile offspring, meaning they have become separate species
What is the difference between natural selection and speciation?
-natural selection involves organisms passing on favourable alleles
-speciation includes natural selection, but uses it to show how new species emerge through the isolation of members within a particular species
What did Gregor Mendel do, and what did he figure out?
-he carried out breeding experiments on pea plants in the mid-19th C
-inheritance of characteristics is determined by a certain “unit” that is passed on to offspring unchanged
Crossed pure-bred green (DD) with pure-bred yellow (dd) to get Dd, and interbred 2 Dd’s to get DD, Dd, Dd, and dd - shows a 3:1 ratio of green:yellow, and that green gene is dominant
Describe how the gene theory was developed over time:
-Mendel with his peas in mid-19th C
-scientists observed the behaviour of chromosomes during cell division in late 19th C - realised that these behaved in a similar way to Mendel’s “units”
-the idea of these “units” being located on the chromosomes was created (now called genes)
-structure of DNA and mechanism of gene function was worked out in mid-20th C
Give some evidence for evolution:
-development of DNA analysis shows that characteristics are passed onto offspring through genes
-fossils, since they show the change in organisms over time
-antibiotic resistance can develop in bacteria
What are fossils?
the preserved remains of organisms from millions of years ago that are found in rocks
Describe 3 ways that fossils are formed:
-absence of one or more conditions for decay means parts of organisms can’t decay (eg preserved in amber/ice)
-parts of the organism get replaced by minerals as they decay, and turn into rock-like substances
-traces of organisms are preserved (eg footprints, burrows, and rootlet traces)
Describe how a fossil usually forms when a sea animal dies:
-sea animal dies and falls to seabed
-gets covered in sediments
-soft tissues decay while bones don’t
-bones are replaced by minerals
What are evolutionary trees?
a method to show the evolutionary relationship between the organisms being studied, where the branches represent the divergence of a species into 2 (speciation)
