Bio Unit Test 2 Flashcards
What is evolution?
The result of changes over time. Natural and Necessary.
Give an example of evolutionary mutations.
Bacteria becoming resistant.
What is a mutation?
Spontaneous, natural changing of the structure of a gene
What are the basis of genetic variation?
Mutations.
The more complex the organism…
…the less mutations occur.
What are the 3 types of mutation?
Neutral, harmful, beneficial.
What is neutral mutation?
One that does not result in advantage or disadvantage.
Give an example of a neutral mutation.
CAA, CAG are both codes for the amino acid called Glutamine.
What is harmful mutation?
Any mutation that makes the individual less successful. It will be selected against and will not accumulate.
Give an example of harmful mutation.
A mutation can disrupt a cell’s life cycle, so that it divides uncontrollably. This is cancer.
What is beneficial mutation?
Any mutation that increases the reproductive success of an organism. It will be selected for, and will accumulate.
Give an example of beneficial mutation.
A mutation that slightly increases the size and robustness of a bird’s beak may allow it to expand its food sources.
Talk about sickle cells.
A certain mutation results in the cells killing each other (sickle-cell anemia). This mutation however does protect the individual from malaria. In this way it is beneficial and more prevalent in places where there are malaria epidemics.
Talk about bacterial resistance.
The bacteria mutate and become resistant to antibiotics. This is beneficial to the bacteria but harmful to the hosts.
What determines if a mutation is good or bad?
The situation. For example: the more human pigment someone has the more protected they are from UV absorption and vitamin D.
When does selective breeding occur?
When humans interfere with natural selection to help breed chosen characteristics that are beneficial to us.
What is selective breeding common for?
Plants (corn) and animals (dogs).
How long does selective breeding take?
A long time, it takes several generations.
What are some ways we selectively breed dogs?
Changing their size and Altering them to better sniff out vermin, hunt birds.
What is artificial selection?
Directed breeding in which individuals that exhibit a particular trait are chosen as parents of the next generation.
What does the process of artificial selection allow us to produce?
New organisms with specific traits.
What was the earliest domesticated animal?
Wolves, modern dogs descended from wolves.
What is the benefit of artificial selection?
It can create a situation with more variability than would occur in nature.
Give an example of a scenario where less variability would occur than in nature because of artificial selection.
Several types of carrots exist but we eat the orange ones because they are crispy and sweet.
What could favoured alleles (traits) be linked to?
A detrimental trait.
What is an allele?
A trait.
What are the limits of artificial selection?
- Having to work with existing traits only.
- Harmful mutations can be passed on along with desired ones.
- If the species becomes too alike, they can be all wiped out by the same disease.
Where does some of the most compelling evidence for evolution come from?
Biogeography.
What is biogeography?
The study of geographic distribution of organisms based on both living species and fossils.
What were the 4 things Darwin observed on the voyage of the Beagle?
- There are many species or plants, birds, insects.
- There are no native amphibians, few land animals.
- There are unique species found nowhere else on earth.
- Theses unique species resemble species on nearest continental land mass.
What were the 4 conclusions Darwin made based on his observations?
- Only these kinds of organisms (plants, birds, insects) can reach remote islands by crossing open waters.
- The amphibians were not able to cross over.
- Over time ancestral species evolved into new geographically isolated species.
- Unique species are descendants of ancestral species from continental land masses.
What are homologous features?
Structure with common evolutionary origins but they may serve different functions.
Why are the bones similar?
Because they share a common ancestor.
Give an example of a homologous developmental structure.
Human embryos have a short bony tail and gill slits.
How are mammal skeletons homologous?
All mammal skeletons have 28 skull bones and 7 neck bones.
What are vestigial features?
Rudimentary and non-functioning features that are homologous to a fully functioning structure.
What can vestigial features be linked to?
A common ancestor.
Give an example of a human vestigial feature.
Goosebumps. They don”t make us warmer because our hair is sparse.
Give 3 examples of vestigial structures in animals (other than humans).
Pigs’ two toes, dogs’ dew claws, whales’ and snakes’ hipbones/pelvis.
How does competition affect individuals in a population?
Certain individuals in a population are favoured by nature.
How are all populations limited?
They are limited in size by their environment (food supply, shelter)
Between who does competition for survival exist?
Between species and within species.
Which organisms will survive?
The best suited organisms will survive (survival of the fittest).
What is the theory of natural selection?
Nature favours the reproductive success of some individuals in a population over others.
Who created the theory of natural selection?
Charles Darwin.
How does natural selection lead to evolution?
Evolution is the result of natural selection over many generations.
What is the story of Darwin’s theory of natural selection?
He spent 20 years amassing evidence but waited to release it because the date was controversial. Darwin received a letter from Wallace who had the same theory so Darwin rushed to publish his theory.
What were Darwin’s 5 key observations?
- In each generation, populations produce more offspring than there are adults.
- Populations do not continue to grow in size.
- Food and other resources are limited.
- Individuals in a population vary.
- Many variations are heritable.
What did people believe in 380 BCE.
That all living things on Earth had been created in their present form and were unchanging. This was based on many religious and philosophical beliefs.
Which scientist believed that species were created in perfect form but changed over time?
Buffin.
What did Buffin believe?
That species were created in perfect form but changed over time.
Who around the same time as Buffin also proposed that life changed over time?
Carl Linnaeus and Erasmus Darwin.
What did E. Darwin suggest?
That all life came from a single original source.
What did Lamarck propose?
That evolutionary change resulted from two distinct principles.
What were the 2 distinct principles Lamarck proposed?
Use and Disuse: Structures that organisms used became longer and stronger, structures they did not use became smaller and weaker.
The inheritance of acquired characteristics: Individuals can pass on their traits that they have acquired during their lives to their offspring.
Why was Lamarck’s theory flawed?
Because these things do not change in your DNA.
How can we still use Lamarck’s discoveries?
All species evolve over time, species can adapt to their environment, and changes are passed on from generation to generation.
What was the first real evidence scientists found?
That fossils demonstrated change in species.
What are most fossils?
Hard impressions in solid rock of once living organisms.
How are fossils formed?
When buried organisms are gradually replaced by mineral deposits. Usually the body will decompose.
What happens if the body sinks to the bottom of a body of water?
It is quickly buried by sediments, preventing decomposition and compressing the body (mineralization).
What happens if oxygen is present during the formation of fossils?
The body would decompose too quickly to fossilize.
What organisms are fossils usually of?
Aquatic organisms.
Why are observations of fossils tough?
because many fossils are unusual and of unknown organisms. Non of currently living organisms.
What is paleontology?
The investigation of prehistoric life through the study of fossils.
Where are fossils usually found?
Unexpected locations, buried very deep.
What did Georges Curvier note?
- That fossils of simple organisms are found in all depths.
- Fossils of more complex organisms are found only at shallower depths.
- Fossils at shallow depths resemble living species more.
- Rock layers contain fossils of many species that do not occur in layer above or below them.
What does it mean if something is buried at a shallower depth?
It was alive more recently than the fossils underneath it.
Who came up with the theory of Catastrophism?
Georges Curvier
What is the theory of Catastrophism?
The pattern of fossils could be accounted for by a series of global catastrophes that wiped out many species on Earth.
Why do fossils get increasingly more complex over time?
Because you can’t take away characteristics, only add them.
What did Charles Lyell note?
That Earth has been changing by the same processes in the past that are occurring presently.
Geological change is slow and gradual.
Is geological change slow and gradual or fast and catastrophic?
Slow and gradual.
Why was Charles’s proposition so radical?
Because his ideas disproved the belief that the Earth was young.
To what does evolution happen with?
With a population not individuals.
When do we say that a population has evolved?
When it is different from the original population in its allele frequency or genetic makeup.
What does difference in genetic makeup result from?
From specific alleles being passed on to the next generation in a non-random pattern.
What are the 3 (technically 5) ways a population can change?
- Genetic Drift (Bottleneck effect, Founder effect.)
- Gene flow.
- Mutation.
Explain Genetic drift.
In small populations alleles can be lost at random from the population.
Why are greater populations less likely to lose the alleles?
If some random event kills 20 % of the population it may kill the ones that have it in the smaller population, but it is unlikely to kills all of the ones who have it in the larger population.
Explain the bottleneck effect.
A large, temporary reduction that usually results in a significant genetic drift (loss of traits.)
Give an example of the bottleneck effect.
There were once 100 000 elephant seals but we hunted them. By the 1890’s there were only 200 elephant seals. NOW, there are 30 000 seals who all descended from those 200 so lots of genetic diversity was lost.
Explain the founder effect.
When a small population colonizes a new area, again causing a limited number of alleles to be present.
What are the 2 types of genetic drift?
Bottleneck effect and the founder effect.
Explain Gene flow.
Individuals moving to a new colony bring their alleles with them and will likely alter the genetic balance in the new colony.
Explain mutation.
The random process of making changes in alleles themselves most mutations appear to be neutral (no visible change) or harmful but a very few will be beneficial.
What are the 4 types of selection?
Stabilizing selection, directional selection, disruptive selection, sexual selection.
What would happen if there was no selection?
The population would become more and more varied over time.
On the selection graphs what does the width of the parabola tell you?
The range
On the selection graphs what does the height of the parabola tell you?
The frequency of individuals in the population with a trait.
Where is the mean value for the trait located?
The highest point of the graph.
Describe stabilizing selection.
common, extreme values for a trait selected against, mean stays the same, range is reduced.
Which is the most common type of selection?
stabilizing selection
Describe directional selection.
Selection favours one of the extremes. The mean shifts up or down and the range is reduced a bit. (lopsided)
Describe disruptive selection.
Selection favours both of the extremes in a population and so the result is two populations each with an altered mean and a reduced range. (double peak)
Describe sexual selection.
Selection favouring good looks/ better reproduction.
What makes faces be considered the most attractive?
Having the greatest number of facial features average to any particular culture/race.
Why are average faces most attractive?
Because it suggests adaptation to its environment and health.
What are some benefits to attractive people?
Their partners tend to be more attractive, they are thought to be more intelligent and sociable by their teachers, given better grades.
What has to happen in order for a population to become different from another?
They must be reproductively isolated. No longer a free exchange of alleles between the two populations.
What are prezygotic mechanisms?
Things that prevent mating or fertilization.
What are postzygotic mechanisms?
Things that prevent development of a zygote.
What are the 5 prezygotic mechanisms?
Ecological isolation, temporal isolation, behavioural isolation, mechanical isolation, gametic isolation.
What is ecological isolation?
Two populations do not exchange alleles with each other because they are in different geographic places/ different places in the same ecosystem.
What is temporal isolation?
Two populations do not exchange alleles because they are only available to exchange alleles at different times.
What is behavioural isolation?
Two populations do not exchange alleles because they do not respond to each others’ mating rituals.
What is mechanical isolation?
two populations do not exchange alleles because of some physical barrier that prevents this.
What is gametic isolation?
Two populations exchange sperm and eggs but chemical markers prevent the eggs from being fertilized by the wrong sperm and so no alleles are exchanged.
What are the 3 post-zygotic isolation mechanisms?
Zygotic mortality, hybrid inviability, hybrid infertility.
What is zygotic mortality?
Even though the zygote is created, it fails to develop to maturity.
What is hybrid inviability?
Even though the hybrid is born, it does not live long or is not as healthy.
What is hybrid infertility?
Even though the hybrid is healthy and vigorous, it is not able to reproduce.
What is speciation?
Creating new species.
How does speciation happen?
When two populations become completely isolated and no longer exchange alleles.
What are the 2 types of speciation?
Allopatric speciation and sympatric speciation.
What is allopatric speciation?
A situation in which the two populations are geographically (before becoming seperate species) isolated prior to them becoming seperate species.
What is sympatric speciation?
A situation where the two populations remain in physical contact with each other but still stop exchanging alleles and become seperate species. (changing of the mind/ no physcial barrier).
