Unit 6 Lesson 3: Genetic Variation and Evolution Flashcards
If every organism had the same genetic makeup, there would be no
evolution
If every organism had the same genetic makeup, there would be no evolution. What whould the world be like if this was true
Instead, the planet would still be inhabited by the first organisms to develop on Earth billions of years ago. Dinosaurs would not have evolved or gone extinct; mammals and human beings would not exist.
What genetic variation
Genetic variation can be defined as changes in the genetic makeup of individuals in a population. An easy way to understand genetic variation is to simply look around at members of your own family. While you and your parents and siblings are all genetically similar, there are many differences among individuals. For example, you may have different colored eyes or hair, be different heights and weights, have differently shaped faces and facial features, think differently, or have different health challenges.
Genetic variation can occur for three reasons: A mutation
a change in genetic information caused by a change in the sequence of DNA
Genetic variation can occur for three reasons: Why and how do mutations happen
Mutations can be caused by a wide range of factors including environmental exposures. A mutation can also be spontaneous, meaning that it occurs for no particular reason.
genes
a sequence of DNA that codes for RNA and/or protein
homologous chromosomes
chromosomes that contain the same genes at the same locations
chromosomes
a strand of DNA that has been wrapped around protein to make it fit into a smaller volume
alleles
a version of a particular gene
Genetic variation can occur for three reasons: Genetic recombination
an exchange of DNA having the same genes between homologous chromosomes that results in new combinations of alleles from multiple genes on the same chromosome
Example of genetic recombination
For example, humans have two copies of each chromosome. One copy is inherited from each parent. Each pair of chromosomes carries the exact same genes in the same locations along the chromosome, but the chromosomes may not have the same allele, or version, of each gene.
recombinant chromosomes
chromosomes that have undergone genetic recombination and have new combinations of alleles
genetic recombination creates new combinations of alleles, which increases
genetic variation
sexual reproduction
a type of reproduction which requires two individuals to exchange genetic material.
Genetic variation can occur for three reasons: How does Sexual reproduction impact genetic diverstiy
Sexual reproduction combines genetic material from two individuals. Offspring inherit a random combination of traits from each parent. In addition, mutations which can occur during sexual reproduction can have a significant impact on genetic diversity.
meiosis
a type of cellular division used in sexual reproduction to produce sex cells, also known as gametes, that have half the number of chromosomes of body cells and a different genetic makeup due to genetic recombination
What happens during meiosis
During meiosis, newly duplicated chromosomes exchange segments with one another during the process of genetic recombination. This means that new combinations of alleles can happen with every generation.
somatic cells
cells that make up the body of an individual as opposed to gametes, which are sex cells
zygote
a single cell resulting from the fusion, or combining, of two gametes during sexual reproduction
Each parents’ somatic cells contain two alleles for each gene. What happen to these alleles during meiosis
During meiosis, these alleles are split between the gametes such that each gamete only receives one of the alleles.
Meiosis: What happens to gametes during sexual reproduction
Finally, during sexual reproduction, gametes from each individual randomly combine to form a zygote.
Meosis: how does sexual reproduction increace genetic varation
Since the process of combining gametes is completely random, each zygote has a unique combination of alleles, one from each parent. This increases genetic variation from generation to generation.
The more genes and more alleles you include, the more ? you can achieve, especially when random fertilization is combined with genetic recombination.
genetic variation
Genetic variation is required for the process of ? to occur.
natural selection
1.
. The term natural selection is sometimes referred to as “survival of the fittest.” What is natural selection
The term describes the process by which the best-adapted organisms survive, thrive, and reproduce, while less well-adapted organisms die out.
Example of natural selction
For example, if birds with long, narrow beaks are best adapted to reach and eat the seeds of fruit, they will be more likely than birds with short, wide beaks to survive, reproduce, and pass along their genes. As a result, there will be more birds with long, narrow beaks living in the environment—until or unless the environment changes.
What would happen to individuals if there was no genetic varation and everyone had the saem traits
Without genetic variation, there would be no difference in the abilities of individuals to survive and reproduce. If every individual had the same traits, then all individuals would have an equally likely chance to survive and reproduce
What has to happen for natural selcetion to lead to the evolution of a population
For natural selection to lead to the evolution of a population, some individuals must be more successful compared to others, and this requires genetic variation.
Can all traits be passed down?
It’s important to know, though, that only inherited traits can be passed along to offspring
Are all amimals be part of the process of natrual slecetion?
only animals that reproduce are part of the process of natural selection.
Does an animal that survies but does not reproduce have an impact on eveolution
an animal that survives but does not reproduce has no impact on evolution.
What is an acquired trait and can it be passed down?
an acquired trait, which is a trait that is not determined by DNA but is developed by interactions with the environment, cannot be passed along to its offspring. A mother, for example, might build up strong muscles, but those strong muscles are not passed along to her child because they were acquired, not inherited.
Is it possible to inhertie a mutation
Some mutations are inheritable.
If the new combination allows the organism to survive longer and produce more offspring, the trait will appear more in the ? of that species.
gene pool
How do you know if a trait is likley to be passed on to futrue generations
The more often the trait appears, the more likely it will be passed on to future generations.
The more often the trait appears, the more likely it will be passed on to future generations. Exmaple
For example, birds with beaks more capable of reaching and eating the seeds of local fruit will grow healthier and produce more offspring than birds with differently shaped beaks. Over time, that trait becomes more common in the gene pool and more likely to be passed on.
gene pool
the genetic information of a population of interbreeding organisms
if the trait is detrimental to reproduction well it still be more likely to appear in the gene pool
However, if the trait is detrimental to reproduction, then it becomes less and less present in the gene pool.
Why does genetic variation occur?
There are three reasons: mutation, genetic recombination, and sexual reproduction.
Genetic variation is caused, in part, by advantageous mutations that are passed along to offspring.
Is this statement true or false?
True; Mutations that give an organism an advantage cause genetic variation in the organism.
Based on what you now know, describe the likely outcome in this situation:
A peninsula was cut off from the mainland as the result of a storm. While birds can fly back and forth to the mainland, no mammals, reptiles, or amphibians can now migrate from the island to the mainland or in the other direction. The animals on the island will, of course, continue to evolve. Which types of genetic variation will continue to impact evolution of birds, mammals, reptiles, and amphibians on the island? What will change and why?
All three will evolve through mutation, genetic recombination, and sexual reproduction. Birds will have a greater variation in their gene pool because they can travel between the island and mainland and might introduce more alleles to the population. The other animals will have a more limited gene pool because only the animals on the island are included.
Archaeologists recently discovered that the remains of many of the survivors of the Bubonic plague of the Middle Ages in London and Denmark share a genetic marker, specifically a variant of the ERAP2 gene. They have one gene from each parent. Individuals who got ERAP2 genes during recombination were 40% more likely to survive the plague. Analyze the impact on the gene pool of this population from the Middle Ages.
People who had the ERAP2 gene survived the plague and were able to live and reproduce, which would cause the ERAP2 gene to increase in frequency in the gene pool. Today, about 75% of the world has homozygous ERAP2 genes.
The video describes a situation in which a mutation (darker wings) helped moths to survive in a changing environment (darker tree bark). The moths that had the darker wings were more likely to live long enough to reproduce, and thus more moths inherited dark wings. Later, the process reversed itself. Explain why the reverse occurred and how this second change relates to the process of evolution.
Cleaner air led to the bark on the trees becoming lighter again. Moths with darker wings were now more visible against the tree bark, so they were more vulnerable to predators. Moths with lighter wings were now harder to see. Moths with lighter wings now lived long enough to reproduce and pass along their lighter color to their offspring. This process is an example of how genetic variation caused by mutation can impact the evolution of a species.
What is genetic recombination, and how does it relate to evolution?
Genetic recombination is the process by which the DNA from two parents combines in a unique way to produce offspring during sexual reproduction. It relates to evolution because it is one of the three ways in which genetic variation occurs. Genetic variation makes it possible for natural selection and evolution to occur.
Genetic variation occurs in every species that reproduces ?
sexually
Over time, if enough organisms with the same advantageous trait survive to reproduce, what might happen to the species?
Over time, if enough organisms with the same advantageous trait survive to reproduce, the species as a whole may evolve.
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It’s important to know, however, that only genetic traits or abilities, which are coded into ?, can be inherited.
DNA
the peppered moth natural slection
In England during the industrial revolution, the peppered moth evolved rapidly to a changing environment. Before the industrial revolution, peppered moths were mostly light in color. A mutation in the gene that produces the pigment melanin, a dark skin pigment, caused some individuals to have a darker color. These individuals were rare in peppered moth populations because the oaks on which these moths lived were white in color, giving the lighter colored moths an advantage and the darker colored moths a disadvantage when predators would come to eat them. The light color, which matched the color of the local tree bark, camouflaged them from predators.
As factories became more common during the industrial revolution and began to produce coal smoke, the color of the tree bark darkened. Light-colored peppered moths were now more vulnerable to predators, while peppered moths that had mutated to a darker color were better protected. Over a relatively short period of time, all of the peppered moths near factories evolved to become darker in color. This evolutionary trend reversed itself as pollution lessened and the environment became cleaner.
This is one of the classic examples of evolution by natural selection. The genetic variation seen in these peppered moth populations gave some moths an advantage and some a disadvantage when it came to surviving and producing offspring. Those individuals that survived better because they were more adapted to the environment produced more offspring, creating a new generation that looks more like the successful individuals. It is important to notice here that adaptations are very specific to the environment. The light color was an advantage when the oaks still had white bark, but this adaptation quickly became a disadvantage when the environment changed.
How did the evolution of the moths from lighter to darker help them solve a problem?
While the tree bark color was getting darker, the moths with light-colored wings were becoming increasingly visible to predators when resting on trees. Individuals that were darker were more likely to survive and the population evolved to become darker and less visible to predators. Evolution helped solve the problem of increased predation by helping the moths to better camouflage themselves.
How might genetic variation and natural selection help to solve the problem of over-population of a species in a particular location?
Genetic variation makes some animals larger, stronger, and more aggressive than others. When animals compete for scarce resources, the fittest animals are likely to get the most food and other resources. As a result, those animals are most likely to live long enough to reproduce. Over time, the species will evolve so that only the fittest individuals survive.
