Unit 6 Exam Study Guide Flashcards
Sometimes a random ______ gives rise to a brown mouse in a population of sandy-colored mice. This adds ______ to the _________.
mutation, variation, population
Volcanic eruptions thousands of years ago created patches of dark volcanic rock. Different ______ of mice in the Sonoran desert are now living in different __________.
populations, environments
What is evolution?
Evolution is change in a population overtime.
What are three steps to evolution?
- Occasionally a mutation gives one member of a population a selective advantage.
- That individual is more likely to reproduce.
- More individuals with the new trait survive and reproduce.
________ change, not _________.
Populations, individuals
In the lava fields, how did the dark-colored phenotype change overtime?
In the lava fields, the frequency of the dark-colored phenotype increased over generations.
_______ is a _______ of _________.
Natural selection, mechanism, evolution
What is natural selection?
The environment “selects” which individuals survive and reproduce. Ex. In the case of the rock pocket mice, the selective pressure comes from both the ground color and predators.
________ is based on the current ____________.
Natural selection, local environment
Can the course of natural selection change?
Yes, the direction of selection can always change. Variation is necessary for change to occur and it must be heritable.
_______ are a result of ____________.
Adaptations, natural selection
What are adaptations?
An adaptation is an inherited trait that allows an individual to better survive and reproduce in its particular environment.
For evolution to happen you need to have these four things:
- Variation
- Inheritance
- Differential survival and reproduction
- Adaptation
What is variation?
Individuals in a population or group differ in some traits.
What is inheritance?
The trait is at least partly inherited so that it can be passed on to the next generation.
What is differential survival and reproduction?
Individuals with certain traits are better able to survive and reproduce in an environment than others (in other words, there has to be selection for that trait).
What is adaptation?
The frequency of the advantageous trait increases in the population over many generations. An adaptation is a trait that makes an organism better suited to a particular environment.
What is an example of evidence of evolution by natural selection?
The frequency of the dark-colored mouse phenotype was high in environments covered with lava and low in sandy environments.
What does evolution have to do with alleles?
Evolution is a change in the frequency of alleles in a population.
What is a gene pool?
A collection of alleles in a population.
True or False: Natural selection is not the only way that populations change/evolve.
True
What are three mechanisms of evolution?
- Migration
- Mutation
- Drift
- Selection
What is migration “gene flow”?
Individuals of a different population move in. That might change the population.
What is Random chance “drift”?
Individuals with a particular trait are killed randomly. The population might change just by chance.
What is selection?
Individuals with a particular trait are less likely to survive in a particular environment. The population might change to become better adapted to the environment.
What is the only mechanism that leads to better-adapted populations?
Natural selection
What mutations provide a selective advantage?
Some mutations create alleles that are beneficial and provide a selective advantage.
What mutations provide a selective disadvantage?
Some mutations create alleles that are harmful and provide a selective disadvantage.
Most mutations are _________.
neutral
Who is the most “fit” in an evolutionary sense?
The one who reproduces the most.
What is fitness?
Fitness is about success at reproducing, rather than exercise and good health.
What determines fitness?
Fitness is determined by genotype. It includes the ability to survive, find a mate, produce offspring and ultimately leave genes to the next generation.
A genotype’s fitness can change depending on the ___________.
environment
What is the random part of natural selection?
Changes in DNA that cause variation are random.
True or false: Individuals do not change; populations change.
True
True or false: Most bacteria is not harmful and live in our skin and gut.
True
What are antibiotics?
Antibiotics are drugs that inhibit or kill bacteria. They are used to treat bacterial infections.
What are antivirals?
Antibiotics are not effective against viruses. Antivirals are used for virus infections.
_________ target __________ without harming ___________.
Antibiotics, bacteria, body cells
How do most antibiotics work?
Most antibiotics disrupt cell structures found in bacteria but not in human cells. (Ex. disrupt bacterial cell wall, ribosomes).
How does resistance develop quickly?
Resistance can develop quickly because bacteria reproduce often (many chances for mutations to occur, and rare alleles can spread quickly).
Using a lot of antibiotics creates an environment where…
resistant bacteria become more common.
The more we use ___________, the greater the ______________.
antibiotics, selective pressure
What are superbugs?
Bacterial strains that are resistant to multiple antibiotics. The main causes are improper use of antibiotics and poor prevention.
Is antibiotic resistance an example of artificial selection or natural selection?
Natural selection
There is a ___________ in areas with malaria.
balancing selection
What is the selection in areas with malaria?
- There is selection against the sickle cell allele because it causes sickle cell disease.
- There is a selection for the sickle cell allele because it protects from malaria.
- This keeps the allele in the population in areas with malaria.
How does malaria cause a selection for different mutations?
Mutations in different genes were selected in parts of the world with high malaria rates.
___________ acts on the __________ that exists in a particular ________.
Natural selection, genetic variation, population
Mosquitos are a ________ on humans because they carry a lot of different _________.
selective pressure, diseases (Malaria, Dengue, West Nile, Zika, Yellow Fever)
What are “vectors”? Give an example.
Mosquitoes are called “vectors” because they don’t get sick from the diseases but can spread them.
What has the WHO tried doing to the mosquito population due to diseases? What happened to these mosquitoes instead?
For years, the World Health Organization tried to eradicate mosquitoes using pesticides. Populations of mosquitoes evolved resistance to pesticides.
Now they are using netting to prevent bites.
What are possible malaria treatments?
- There are drugs that can treat malaria but they are not available to everyone.
- In 2021, the first malaria vaccine was approved by WHO has an efficiency of about 50%.
- A more effective vaccine is in Phase II trials; about a dozen vaccines are in different stages of development.
Some adults in any population have the lactase enzyme and some adults don’t. The variation is _________.
inherited
What is the lactase persistence in different cultures?
- In cultures that did not use animal milk: no advantage to producing lactase as an adult, so there is selection against lactase.
- In cultures that started to use animal milk (pastoralist cultures): advantages to producing lactase as an adult, so there is a selection for lactase.
The lactase trait is an _______ because it became more common in pastoral populations.
adaptation
__________ is a change in allele frequencies _________ over time.
Evolution, in a population
What is an evolutionary adaptation?
An evolutionary adaptation is a trait (allele) that arose and became common in a population by natural selection.
What is acclimation?
Individuals can also “adapt” to an environment. This is called acclimation. Acclimation is a physiological change that is not lasting and is not inherited.
What are three examples of acclimation:
Changes do not last if the individual leaves the environment and they can not be passed to offspring.
1. Increasing red blood cell production in response to being in high altitude.
2. Tanning in response to sun exposure.
3. Sweating in response to body temperature rising.
What are cultural adaptations?
Humans are able to live in many types of environments without having many genetic differences among populations. Humans have used technology and innovation to thrive in adverse environments- cultural adaptations.
Is skin color an inherited trait?
Yes, and it’s determined by many genes and the environment.
What are humans an example of?
Humans are primates (group includes monkeys, chimpanzees, and gorillas).
What do nonhuman primates have in common?
All nonhuman primates are covered in thick body hair. The last common ancestor we share with our closest primate relatives was probably also covered in thick hair.
What determines the color of human skin?
The type of visible radiation reflected.
What is the harmful effect of radiation from the Sun?
It damages DNA in skin cells.
What’s the main function of melanin in humans?
Protecting cells from DNA damage due to UV radiation.
Skin color is a __________ trait.
continuous
How does the amount of variation in the MC1R gene relate to natural selection?
The lack of variation in the MC1R among African populations compared to other countries shows that melanin provides these populations an advantage.
What is selective breeding?
Humans select individuals with a particular trait and mate them to get more individuals with that trait.
What are examples of artificial selection?
Domesticated crops and animals
Many organisms that we eat today came from __________ that were ___________ to have traits that were useful to humans (ex. easier to grow and harvest, easier to eat, tasted better).
wild ancestors, selectively bred
One ______ evolved into many _______.
wild ancestor, varieties (Ex. wild mustard plant evolved into cauliflower, broccoli, cabbage)
What are genetically modified organisms?
Genetically modified organisms are a new way humans “select” desirable traits.
How does technology create genetically modified organisms?
Because all organisms use the same genetic language (“code”), technology allows us to insert a gene from one species into another to give the modified organisms a new trait.
What are some of the biological effects of UVB radiation?
A. Increased synthesis of vitamin D
D. Increased DNA damage in skin cells
E. Decreased folate in blood
Traits are inherited _________ of one another.
independently
________ and _______ during ______________ produce new combinations of alleles each generation.
Crossing over, independent assortment, meiosis + fertilization
What is speciation?
It’s the formation of new species.
How does speciation occur?
It occurs when an ancestral species evolves into two or more species. Usually takes a very long time.
True or false: Evolution can happen over a short period of time as the frequency of alleles in a population changes. But not all changes lead to new species.
True
What are species?
A species is a group of similar organisms that can reproduce (exchange genes) and produce offspring that can also reproduce.
Some species occasionally interbreed and produce ________.
hybrids
What are three facts about the Galapagos Islands?
- Group of 14 islands west of South American mainland.
- Famous because they were visited by Darwin.
- They are a natural laboratory to study how species evolved over a short time period in a new environment without much human disturbance.
What are three facts about the Galapagos Finches?
- The islands are home to 13 different species of finches.
- Different islands have different finch species. Some species are found on more than one island.
- The finch species are endemic to the Galapagos, which means that they are found nowhere else in the world.
What do we call a trait that makes organisms more likely to survive and reproduce in their environment?
Adaptation
The different beak shapes/sizes on the Finich’s of the Galapagos Islands are ___________ to the ___________.
adaptations, environment
What are two factors that prove that the Galapagos finches are different species?
- Members of one species don’t typically mate with members of another species because they have different songs and appearances.
- That means there is no “gene flow” between populations. They don’t mix genetic material; they are separate species.
Scientists can figure out evolutionary relationships by looking at these three factors:
- Appearance (anatomy)
- Behavior
- DNA
What are evolutionary trees?
Using DNA and morphological evidence, scientists construct evolutionary trees (phylogenies) to predict the evolutionary history of related species.
What do evolutionary trees show?
- When speciation events happened
- Relatedness of species
In evolutionary trees, species on a given branch are more…
closely related than species on other branches- they share a more recent common ancestor.
How did speciation in finches occur?
- Finches from the mainland population came to one of the islands. Eventually sub-populations spread to other islands.
- Isolated from one another, the populations were subjected to different selective pressures on each island (available food sources, predators).
How do species become separate species?
If the changes that occurred while isolated included traits that impacted mating, then they became distinct species. (Different species do not mate or exchange genes).
What are the three steps of speciation?
- Speciation begins with reproductive isolation (no gene flow). Can be a geographic (physical) barrier.
- Once isolated, the two populations can take separate evolutionary paths.
- Finally, some changes produce intrinsic barriers to reproduction. They are distinct enough not to mate successfully.
Species are kept separate by intrinsic reproductive barriers. These intrinsic reproductive barriers include these four factors:
- Behavior (different mating rituals; mating time differences)
- Anatomy (reproductive anatomy is different)
- Habitat use (adapted to different environments)
- Genetic (sperm cannot fertilize the eggs)
Sometimes species can mate but the _____ offspring is not ____________.
hybrid, viable or sterile
What is a common gene pool?
Members of the same species interbreed and share a common gene pool.
When populations of a species are isolated, _______ can become very different.
allele frequencies
Large differences in the gene pool can exist, even if…
members of two species don’t look that different.
True or False: Speciation can happen in the same area without a geographic barrier.
True
If a modern species originated hundreds of millions of years ago and it looks identical to those fossils, has it evolved?
Yes. All species evolve over time
DNA provides a __________ to estimate when two species split/diverged.
molecular clock
What are homologous genes?
Homologous genes are genes in different species that have similar DNA sequences and may produce proteins with similar functions.
What is the universal genetic code?
We all use the same genetic language- a universal genetic code. The code for making proteins was established early in the history of life and passed down to all living things.
What are homologous structures?
Homologous structures are shared features among species that are inherited from common ancestors.
What are vestigial structures?
A feature in an organism that was useful for an organism’s ancestor, but has become reduced/less functional over time. Organisms still have reduced features due to common ancestry.
What is homologous development?
Ex. All vertebrate embryos have a tail and gills. Some species of snakes have hind limb buds as early embryos but lose the buds as adults.
What is a fossil record?
A fossil is any trace of a living organism (body, part of body, burrow, footprint) preserved over geologic time.
How do fossils provide a history of life?
Fossils tell us about the organisms that have existed in the past and how they lived.
How do scientists track a geological record?
- The surface of the Earth is made of layers of rocks. Fossils found in lower layers were buried earlier and thus must be older than fossils in higher layers.
- Scientists can also date rock layers by measuring radioactive elements found in rocks.
What are transitional fossils?
- Fossils of organisms that show a mix of traits of the ancestor and its descendants.
- Big evolutionary changes happen in small steps.
- Many examples of transitional forms in the fossil record provide overwhelming evidence for change over time.
How do extinction and speciation go hand in hand?
- Typically, there is a constant baseline rate of extinction (species fail to adapt to environmental changes) and speciation.
- At certain points in time there have been mass extinctions, where a large percent of species die out in a geologically short period of time.
- Large amounts of speciation tend to occur after mass extinctions.
- These two processes determine the diversity of life on Earth.
Why are we concerned about climate change as it relates to extinction? (Three points)
- We are currently in the 6th mass extinction due to human activity.
- Climate change is occurring at a rapid rate. Evolution takes time and many species will not be able to adapt.
- Life on Earth always rebounds, but it looks different from how it did before.
Why isn’t there a lot of genetic diversity among humans? Give four reasons.
- There are only one species of modern humans.
- The first evidence of our species (Homo sapiens) is about 300,000 years ago. We’re a young species.
- Populations have been moving to locations outside of Africa for only 60,000 years.
- During that time there has been a lot of movement and mixing of populations so there are a few genetic differences among populations.
If you compare any two humans from different parts of the world, their DNA will be ____ the same.
99.9%
What is genetic ancestry?
Genetic ancestry refers to recent human history.
What are ancestry tests?
Ancestry tests compare rare variations that are more common in some geographic areas.
What can ancestry tests tell you?
Ancestry tests can tell you about your ancestor’s recent geographical history.
Do human populations have adaptations?
Human populations show some adaptations to different geographical areas and environments, but they are not unique to any one population and they do not correspond to the socially defined categories of race.
What is race?
Race is a human invention without a scientific basis. The scientific consensus is that there are no biologically defined races. The human race is an invention of human society, but it can have biological impacts on people due to unequal access to healthcare, exposure to pollution, stress, and nutrition.
What is the theory of evolution?
The theory of evolution is a unifying theory of biology, meaning it is the framework within which biologists ask questions about the living world.
What did Darwin and Wallace reason to believe?
Offspring with inherited characteristics that allow them to best compete for limited resources will survive and have more offspring than those individuals with characteristics that are less able to compete.
A mutation can have one of three outcomes on the organisms’ characteristics (or phenotype):
- A mutation may affect the organism’s phenotype in a way that gives it reduced fitness- lower likelihood of survival and reproduction.
- A mutation may produce a phenotype that increases fitness.
- Many mutations, called neutral mutations, do not affect fitness.
What is the bottleneck effect?
Natural or human-caused events, such as a disaster that randomly kills a large portion of the population, known as the bottleneck effect that results in a large portion of the gene pool suddenly being wiped out.
What is the founder effect?
If some portion of the population leaves to start a new population in a new location or if a population gets divided by a physical barrier. Those individuals are unlikely to represent the entire population, resulting in the founder effect.
In a phylogenetic tree, what is a node?
The point where a branch splits is called a node and represents the common ancestor from which descendant species diverged. Many phylogenetic trees have a single branch point at the base representing a common ancestor of all the species in the tree.
