B15 - Genetics & Evolution 2️⃣✅ Flashcards
(40 cards)
What were the 3 main things Darwins theory of evolution by natural selection proposed?
- Individual organims within a particular species show a wide range of variation & characterisics
- Individuals with characteristiscs most suited to the environment are most likely to survive and breed
- The characteristiscs that have enabled these individuals to survive are then passsed onto the next generation
Give three reasons why Charles darwins theory of evolution by natural selection was only gradually accepted in the 1800s society in which it was released into
- The theory challenged the idea that God made all the animals and plants that live on Earth
- At the time there was insufficient evidence to convince many other scientists
- The mechanism of inheritence and variation was not understood/ known until 50 years after the original theory was published
What was Jean-Baptiste Lamarck’s theory?
The theory of aquired characteristics
* That if an organism wanted something enough it would aquire the desired characteristic e.g. giraffe essentially wanted to reach leaves higher so stretched it’s neck to do so
What is natural selection?
When the environment decides which genes/ characteristics are advantageous and allow for organisms to thrive & therfore breed to pass on the desired characteristic
What determines organisms the same species?
If they can reproduce to produce fertile offspring
How was lamarack’s theory proven wrong?
By the existence of modern genetics as we now know that aquired characteristics not affect the DNA sequence of the organism, and cannot be passed down from one generation to the next.
What did Wallace do to contribute to the theory of natural selection?
As well as Darwin, he independently reached a very similar conclusion for evolution by natural selection as Darwin did + theorys revolving around speciation that we use today.
Did Wallace & Darwin ever compare research?
Yes, they both presented a joint paper together, providing additional support to the theory.
What did Wallace mainly contribute to revolving around speciation?
The evolution by natural selection and therfore speciation between organisms that are of very similar characterisitcs but have different phenotypes - different colours. Wallace was especially known for his work on colouration of species depending on their environement
What is speciation?
When 2 organisms of the same species undergo changes (evolution) via natural selection that make them each so different that they can no longer reproduce to produce fertile offspring, therefore deeming them separate species
What is the structure/ flow chart for Evolution by natural selection?
(can also be applied to answering questions)
What three things did mendel test for in his experiments?
- Colour of pea pods
- Length of pea plant
- Colour of flowers
What did mendel discover during his experimentation?
- Characteristics in plants are inhertited/ are determined by ‘heriditary units’
- Hereditary units are passed to offspring, unchanged, but one from each parent
- Heriditary units can be dominant or recessive (If both dominant and recessive, domainant will be expressed, you require 2 recessive allelels in order for the recessive characteristic to be expressed)
Why was it that mendel’s work was only aknowledged/ used after his death?
Because in the 1800s they did not have any idea of chromosomes/ genes/ DNA
When was mendel’s work realised to be correct/ the foundings for genetics?
In the early 20th century is was observed that chromosomes & mendells ‘units’ behaved in similar ways - This lead to the idea that the ‘units’, now genes were located on the chromosomes
What causes speciation to naturally occur?
Changes in the natural environment/ separation of 2 groups of the same species due to an environmental change
How does speciation work?
After separation, alleles for characteristics that enable the organisms to surive and breed sucsessfully in the new envrionment will be selected/ passed on. These alleles are going to be different from those that gave sucsess in the original envrioment as it would have been different. As a result of the selection of the new alleles the 2 separate populations would increase in genetic variation and change, so much so that they can no longer interbreed to produce fertile offspring, implying that a new species has formed and speciation has occured
What is extinction?
When there is no remaining individuals of a species still alive
What are 4 factors that contribiute to extinction of species?
- the environment changes too quickly and the species cant adapt in time so dies
- A new species/ predator kills them all or out competes them, starving them of resources
- A new disease comes and wipes them all out
- A catastrophic event occurs such as asteriod that wiped out dinosaurs
What are the 3 main methods of fossilisaiton?
- Gradual replacement by minerals
- Casts + impressions
- Complete preservation (no decay at all)
How does fossilisation by gradual replacement of minerals work?
When parts of an organism such as teeth/ bones decay very slowly and over time are replaced by minerals. Therefore leaving behind rock-like substances in the exact same shape & size of the organsim, but just made of rock/ mineral.
How does fossilisaiton by cast + impressions work?
When an organism is burried in a soft mateiral such as clay, as the clay hardens, the organism decays, leaving behind a gap in the clay in the same shape/ size as the organism + impressions are when things such as footprints are preserved
How does fossilisation by complete preservation work?
When an organism gets trapped in a material such as amber & it then hardens - due to the lack of oxgyen and moisture, the organism remains completly in tact and doesnt decay, perfectly and completly preserving the organism
What are 4 places in which fossilisation by complete preservation of organsism can occur?
- Peat bogs
- Glaciers
- Tar pits
- Amber
