Evolution - Development of the Theory Flashcards
How is evolution measured?
It is measured at the population level
What is evolution?
Its a descent with modifications or noticing changes in allele frequencies overtime
What did Darwin based his theory of natural selection on?
He based his theories on 1. Over reproduction , 2. Individual variation
What is Over reproduction?
When there is an excessive number of off-springs which led to struggles of existence
What is individual variation?
When you notice different things in different organisms and notice that all organisms had so much variation and that they are heritable.
Define heritable?
When genes are passed from one generation to the next
What is modern synthesis?
Fusion of genetics with evolutionary biology (when your interacting genetics with evolution)
What are the essentials of evolution?
All organisms vary genetically within a population so if a trait is not heritable than natural selection will not act upon that variation
Traits must also be heritable
Favourable traits with allow organisms to survive and reproduce to pass their genes on to the next generation
Major change in evolution normally takes long periods of times
What does misconception of evolution mean?
Its essentially what people think evolution is, but really its not always true
Evolution of theory is about the origin of life (miscon)
Evolution mainly focuses on how life changes after its origin and how life branches our and diversify
Organisms are always getting better (miscon)
The idea of evolution is not about organisms reaching up to the very top of perfection. NS will just simply weed out individuals who seem to be unfit for a particular environment.
Evolution is NS (miscon)
Evolution is not the same as NS, NS is the mechanism focused on surviving on a specific environment
Evolution means life chaned by “chance” (miscon)
NS is not random. Mutations is the ultimate source for genetic variation that selection will act upon however, NS itself will simply choose which variant is most fit for the environment so it wont pick by choice. However the idea of mutation may be random
Organisms “try” to adapt (miscon)
Organisms do not try to adapt however NS leads to adaptation but the process itself does not involve “trying”
NS gives organisms what they need (miscon)
NS does not ever know what a species need they do not have senses. If a population happens to have genetic variation which will allow some to survive better than others, then those individuals will leave behind off-springs which will allow the population to evolve.
Selection acts for the “good of species” (miscon)
Selection happens to individuals, not species. The idea of Altruistic is sometimes believed that NS promotes this behaviour, but that’s not true. NS will simply choose individuals from a population they believe is the most fit. The reason why altruistic may happen could be because they will get repaid for that act and that behaviour can be favoured by NS. Kin selection is also involved in this.
What is kin selection?
When genes are being passed on whether its directly or indirectly by saving your relatives and warning them of predators so they are able to survive and reproduce
Evolution occurs slowly (miscon)
Not necessarily true it can actually occur rapidly depending on factors
Selection acts on individuals (miscon)
Does not act on individuals but the change is acted upon population. So you won’t notice evolution in your own lifetime but can be recognized in then entire population
NS is not directed (miscon)
Based on the environment the organisms is living in
Evolution by natural selection is a random process (miscon)
Mutations themselves might occur randomly in a genome but the natural selection is not random. It selects individuals in a population with a certain trait
Traits arise in response to a change in the environment (miscon)
If a certain mutation arises and is promoted, NS will act upon it
Selection acts on the genotype because that is what is inherited (miscon)
Selection acts upon the phenotype but phenotype is based on the genotype, so responding change will occur in the genotype
Humans have stopped evolving (miscon)
No we did not stop evolving.
Define Natural selection
The process by which random evolutionary changes are selected for by nature is a consistent, non-random , orderly way
Evidence regarding evolution
There has been debates about how evolution took place, there has been gaps in fossil records which may indicate evolution, Evolution is constantly being refined, Darwinism’s rejection, all his ideas worked under NS even though he had no idea about it
What is adaptation?
It is a trait or characteristic of an organism that increases its fitness relative to individuals without the trait
What is fitness?
The ability of an individual to survive and reproduce in it’s enviornement
What are Darwin’s 4 Postulates?
- Individuals within populations are variable (because of mutations, shuffling alleles, new combinations, individuals within populations are variable for many traits)
- The variations among individuals are, at least, in part, passed from parents to offsprings ( individuals pass their alleles on to their offspring intact)
- In every generation, some individuals are more successful at surviving and reproducing than others
- Survival and reproduction of individuals is not random (the individuals that survive and reproduce are those with the alleles that best adapt them to their environment)
Modern Synthesis
Integrating genetics with Darwin’s 4 postulates-
So gradual evolution results from small genetics changes that are acted upon NS, but he did not know what genetic was
The origin of species and higher taxa (macroevolution) can be explained in terms of NS acting upon individuals (microevolution)
You can have very small phenotypic changes lead up to larger ones
What are the road blocks for evolution?
Would ask questions like; How was variability generated in populations? Did not understand how phenotypes were essentials to reproductive success
How were “variations” passed onto the offspring? ; Did not know how genetics worked and how variations passed on
Age of earth; They assumed earth was only a few thousands years old but then with the “Lord Kelvin” calculations, it showed up that the earth was a lot older than we thought
What was Darwin’s finches case study?
Darwin would travel around and he started studying Finches. They were a collection of birds who derived from Central or South American common ancestors. He noticed different variation in beak sizes and decided to analyze and study what gene was responsible for variation in beaks.
What gene was responsible for variation in beaks of Finches?
(BMP4) Bone Morphogenic Protein 4
What did larger beaks signify?
More expression of BMP4
What did smaller beaks signify?
Less expression of BMP4
Analysis of graphs based on beak size
So in a graph, if you noticed a bunch of markers clustered together, that signify that genetics was relatively strong. If we noticed the markers spread all across the graph, that signifies that the environment is more important and that genetics was not that strong.
1976 and 1978 survival rate of finches
In 1976 there was 751 finches. Only 90 out of those 751 survived by 1978. The other 85% did not survive. They noticed the 90 who did survive had an average beak size of 10mm. So the survival and reproduction was not random, it was based on the fittest finches.
Did the finches evolved from 1976 and 1978?
Yes the Finches did evolved. In 1976, the average beak size of the finches was about 8.8mm while by 1978, the average beak size was 9.8mm/10.0mm. That means the average phenotype in the offspring did evolve.
Was there variations on survival and reproduction for the finches?
Essentially, the variation of survival and reproduction was literally all based on what the environment provided. If it provided a lot of nutrients, food, water, then Finches would be able to survive and later on reproduce.
Explain how NS is not forward looking and how it is not random?
NS does not have end end game. As new generation arises and genetic variability has been expressed, NS will act upon the most fit in that specific population and generation. Selection is always evolving with the environment so it is always going to be based on the current environment. Because some generations may still be adapted to previous environments that is not fit for their CURRENT environment. NS is random, the mutations affecting genotype may be, which may express phenotype differently and NS will act upon that but NS in general is never random. NS is also NOT progressive. Newer and newer generations are not always going to be considered better than their previous generations. The population may cope better with their new environment but they are not exactly considered a better fit generation.
Explain how fitness is not circular?
Fitness will vary within time. What was considered fit last generation may not be considered fit this generation
Explain how selection acts upon individuals
Selection will act about phenotype which is partially by the genotype. Before selection the average beak size was from smaller to bigger, then when the smaller beak birds die, it was based on larger beaks and then the average beak size on the next generation was just slightly bigger
Explain how NS is not “perfect”
- Always tradeoffs
- Fish with better reproductive system, swim slower = caught by predators
- Fish was smaller reproductive system, swim faster = escapes predators
There is always a trade off between sexual and reproductive selection you will rarely get that perfect generation that has both
