Honors Biology Evolution
“species are fixed”
A pre-darwinian idea
All species of organisms have been the same since they first appeared on the planet
adaptations
Feature that allows an organism to better survive in its environment
Adaptations can lead genetic change in a population over time
allele frequency
Measure of how common a certain allele is in a population
Calculation for any given allele’s frequency:
1. count number of times an allele occurs in a gene pool
2. divide part 1 by the total number of alleles in a gene pool for a gene (Part/whole)
analogous structures
Structures performing similar functions but are not similar in origin, no close common ancestry
i.e. bat wing and butterfly wings
Found in organisms that have similar environmental needs so have similar adaptations using different body parts
NOT evidence for common ancestry
artificial selection (know the definition & an example; For instance, where did every single dog breed come from?)
Process by which humans change a species by breeding it for certain traits
Humans directly manipulate variation within population
Humans act as selective agent
Over time, new varieties/breeds can be produces as traits are refined
For example, all dog breeds are descended from a species of gray wolf
binomial nomenclature
Scientific naming of species where have two names written in Latin
Genus ex. felis
Specific epithet ex. cactus
Felis Catus =species
biogeography
The study of the distribution of species and ecosystems in geographic space and through geological time. It looks at how and why different plants and animals are found in certain areas and not others.
Georges Louis Leclerc De Buffon was the 1st to use biogeography as evidence of evolution, proposed idea that species share ancestors instead of arising separately
bottleneck effect
Genetic drift that results from an event that drastically reduces the population size and variation
Population size is drastically reduced by chance event (earthquake, flood, etc.l; more recently humans have affected populations to the extreme through overhunting, habitat destruction, etc.)
By chance, some alleles in gene pool stay and become fixed and other alleles are lost and become eliminated
catastrophism
Theory that states that natural disasters such as floods and volcanic eruptions shaped earth’s landforms and caused extinction of some species
George Cuvier explained his observations with this theory, thought disasters changed landforms and lead to extinction and the same time
cladogram (know term & be able to read)
A diagram used to show relationships among organisms
It represents a hypothesis about the evolutionary history of a group of organismsbranch: each branch represents a lineage
Nodes: each node represents the most recent common ancestor of the lineages that branch from it
reading a cladogram: start from the base or root and move towards the tips. The close two organims are on the cladogram, the more closely related they are
directional selection
A type of selection that favors phenotypes at one extreme of a trait’s range
Causes a shift in population’s phenotypic distribution as a once rare phenotype becomes more common
Mean value of trait shifts in the direction of more advantageous phenotype
ex. drug resistant bacteria
disruptive selection
Occurs when both extreme phenotypes are favored, while individuals with intermediate phenotypes are selected against by something in nature
Middle of distribution is disrupted
See more individuals at both extremes and fewer individuals in intermediate state
ex. feather color in male lazuli buntings
evolution (know definition from text; know level of organism this goes along with)
Process of biological change by which descendants come to differ from their ancestors
Occurs at population level, not individual organisms
fitness
A measure of ability to survive and produce more offspring relative to other members of population in a given environment
fossils
Traces of organisms that existed in the past
Observation made by Darwin was that fossils showed evidence of species changing over time
founder effect
Genetic drift that occurs after a small number of individuals colonizes a new area
New population is established (colonized) by a small group of individuals
Small gene pool may mean less genetic variety
gene flow
Movement of alleles from one population to another; aka exchange of genes with another population
gene pool
Combined alleles for every type of allele at every locus of all of individuals in a population
genetic drift
Change in allele frequencies due to chance (random, unpredictable event) alone
Typically occurring in populations that are small, and more likely to be affected by chance
Causes a loss of genetic diversity in a population
Two processes commonly cause populations to become small enough for genetic drift to occur: bottleneck effect and founder effect
genus
The term is used to classify a group of related species. It’s one level above species in the hierarchy of biological classification
Hardy-Weinberg equilibrium
Condition in which a population’s allele frequencies for a given trait do not change from generation to generation
Model created from research of Godfrey Hardy (mathematician) and Wilhelm Weinberg (physician)
It is a tool to measure changes in allele frequencies over time
heritability
Ability for a trait to be passed down from one generation to the next
homologous structures
Similar structures found in more than one species that share a common ancestor
i.e. human arm, bat wing, dolphin flipper, cat foreleg, all have similar internal bone structure
Structures frequently do not have a similar function
Unlikely that several species have similar ancestry if each species evolved independently
hybridization
The crossing of two different species that share common genes
It may happen between many groups of birds and mammals when similar species live in close proximity to each other and individuals can’t find mates within their own species
inheritance of acquired characteristics
Hypothesis that changes in the environment cause organisms’s behavior to change, leading to a greater use or disuse of some body parts or organs. Enhanced or reduced features are inherited by offspring
Jean-Baptiste Lamarck
interspecific variation
Differences among individuals from different species
intraspecific variation
Differences among individuals from the same species
microevolution
The observable change in the allele frequencies of a population over time
Occurs within a single population
Natural selection can lead to this
Evolution works on POPULATION LEVEL
migration
mutation
Random changes in DNA of a gene
Change can form a new allele
Mutations in reproductive cells can be passed on to offspring
natural selection
Mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals
Individual organism LEVEL!!!
normal distribution
Type of variation in which the frequency is highest near the mean value and decreases towards each extreme end of the range
For some traits, all phenotypes provide an equal chance of survival; therefore, you see a normal distribution when looking at the variations collectively.
Traits in the middle are most common, traits at the extremes are less common
paleontology
Study of fossils or extinct organisms
phenotype
Expression of a trai
Phenotypes are produce by one or more genes
population
Individuals that belong to the same species that are in the same place at the same time
recombination
(crossing over coupled with laws of segregation and independent assortment; random fertilization too)
Most occurs during meiosis
Gametes form from each parent’s alleles and can arrange in new ways
Shuffling of alleles results in different genetic combinations
species
Group of organoms so similar to one another that they can reproduce and have fertile offspring
specific epithet
The second part of the scientific name in the binomial nomenclature system.
stabilizing selection
The intermediate phenotype is favored and becomes more common in the population
See more intermediate individuals build up in the population
Distributin becomes stable at intermediate phenotype, no shifting to the extreme
ex. gall fly and its predators
uniformitarianism
Theorized geological processes that shape earth at an ongoing, constant rate
Associated with Charles Lyell
variation
Difference in the physical traits of an individual from others in the group to which it belongs (i.e.., fur color, eye colo, height, etc.)
vestigial structures
Remnant of structure that may have had important function in species’ ancestors, but has no clear function in the modern species
i.e. human appendix, whale hip-bones, snakes pelvic bones, wings of an ostrich
Takes many generations for the organs/structures to shrink
Scientists consider vestigial structures among most important examples demonstrating how evolution works
Know the following people and their contributions to science and any possible ideas that helped Darwin come up with his theory of natural selection.
Carolus Linnaeus
1700s
Developed a classification system for all organisms known, binomial nomenclature
Linnaeus’ system grouped organisms by similarities and reflected evolutionary relationships
Linnaeus rejected that organisms were “fixed” and suggested change could come from hybridization to form new organisms
Georges de Buffon
1st to use biogeography as evidence of evolution
Proposed idea that species share ancestors instead of arising separately
Noticed fossils of extinct organisms had some similarities with existing organisms
Noticed even though geographic areas were similar each had unique wildlife that was similar to wildlife in other areas
Suggested that Earth was much older than 10,000 (-80,000)
Erasmus Darwin (Darwin’s grandfather)
Born 1731
Proposed all living things were descended from common ancestor
Proposed more-complex forms of life arose from less-complex forms
Jean Baptiste Lamarck
Early 1800s
One of 1st to suggest humans evolved from lower species through adaptations over time and came up with idea of vestigial structures
Suggested evolution as an explanation for Buffon’s observations
Lamarck’s important contribution: proposed that changes in physical characteristics could be inherited and were driven by environmental changes over time.
Problems:
Did not propose how traits were passed on to offspring; use/disuse of body parts does not alter the organism’s DNA
Lamarck is unfairly criticized for being wrong about method of evolution
George Cuvier
Thought species could not change, but did think species could go extinct
Studied layers of rocks and the fossils within each
Noticed fossils in deepest layers were different from fossils in upper layers
Noticed newest fossils were in more recently deposited sediments
Explained observations via theory of catastrophism
Thought disasters changed landforms and lead to extinction at same time
James Hutton
Later 1700s
Proposed changes in landforms resulted from slow changes over a long period of time -gradualism
Laying down of soil or creation of canyons by rivers cutting through rocks happened slowly over long periods of time
(Darwin would later use this idea of gradualism in reference to organisms)
Charles Lyell
Early 1800s
Theorized geological processes that shape Earth occur at an ongoing, constant rate (uniformitarianism)
Proposed that small gradual changes over millions of years could account for major geographic features (mountains, canyons, etc)
This combined with theory of gradualism from Hutton gave strong evidence for a very old Earth
Over time, replaced idea of catastrophism
Thomas Malthus
Malthusian theory: he proposed that populations grow exponentially, while food production grows arithmetically. This means that if the population keeps growing, it could outstrip food supply, leading to famine and hardship
Malthus’s ideas influenced Charles Darwin and his theory of natural selection. Darwin realized that the competition for limited resources could drive the evolution of species, as only the fittest individuals would survive and reproduce
Alfred Russel Wallace
Co-discovery of natural selection: Wallace independently conceived the theory of evolution through natural selection
In 1858, he sent an essay outlining his ideas to Charles Darwin, which prompted Darwin to publish his own work on the subject. This led to the joint presentation of their findings to the Linnean Society of London
Fieldwork and observations: Wallace conducted extensive fieldwork in the Amazon River basin and the Malay Archipelago. His observations of the diverse species in these regions provided crucial evidence for the theory of evolution
Influence on Darwin: Wallace’s essay on natural selection, along with his extensive field observations, provided additional support and urgency for Darwin to publish his own ideas. Their correspondence and collaboration helped refine the theory.
Natural selection occurs on what level of organisms? Why (what does it work directly on…)?
Natural selection occurs at the level of the individual organism. It works directly on the phenotype, which is the observable traits or characteristics of an organism. These traits can include things like size, color, or behavior.
Phenotype expression: the phenotype is the result of the interaction between an organism’s genetic makeup (genotype) and its environment. Natural selection acts on these traits because they affect an organism’s ability to survive and reproduce in its environment
Survivial and Reproduction: individuals with traits that are better suited to their environment are more likely to survive and reproduce. This means they can pass on their advantageous traits to the next generation.
Population changes: over time, these advantageous traits become more common in the population, leading to evolutionary changes
Evolution occurs on what level of organisms?
Evolution occurs at the population level of organisms. This means that changes in traits and genetic makeup happen over generations within a group of the same species living in a particular area. Individual organisms don’t evolve; instead, it’s the population as a whole that changes over time due to factors like natural selection, genetic drift, and mutations.
Know the components of a species name under the system of binomial nomenclature (genus, specific epithet, and species).
Genus: this is the first part of the name and is always capitalized. It groups species that are closely related. For example, in Homo sapiens, “Homo” is the genus
Specific epithet: This is the second part of the name and it is not capitalized. It identifies the species within the genus. In Homo sapiens, “sapiens” is the specific epithet
Species: The combination of the genus and specific epithet together forms the species name. So, Homo sapiens is the full species name for humans.
Know about evolution by means of inheritance of acquired characteristics. Know examples of inheritance of acquired characteristics.
The idea of evolution by means of the inheritance of acquired characteristics was proposed by Jean-Baptiste Lamarck. He suggested that traits developed during an organism’s lifetime could be passed on to its offspring. For example, if a giraffe stretched its neck to reach higher leaves, Lamarck believed its offspring would inherit a longer neck.
Be able to list the key observations made by Darwin and know information about each.
Great amount of variation among similar species, interspecifc, intraspecific
Differences seem to be well suited to an organism’s environment and diet
adaptations can lead to genetic change in a population over time
Fossils showed evidence of species changing over time
Argentina: fossils of huge organisms like Glyptodon found that suggested ancient species gave rise to living species, suggests that species aren’t fixed and have change over long periods of time
Andes Mountains: found fossils shells of marine organisms
Then experienced earthquake and saw underwater lands moved above sea level and this explained Andes situation
Supported Lyell’s ideas of small gradual changes add up over time to account for major geographic features
Supported idea of ancient earth
Geographically close species appear to have close common ancestry
temperate species on South America tended to more closely resemble tropical species on same continent.
More so than temperate species on South America and temperate species on Europe
Overproduction: Most species produce more offspring than can survive. This leads to competition for resources like food, water, and shelter.
Survival of the fittest: Individuals with traits that give them an advantage in their environment are more likely to survive and reproduce. This is often called “survival of the fittest”
Reproduction: The individuals that survive pass on their advantageous traits to their offspring
Adaptation: Over many generations, these advantageous traits become more common in the population, leading to adaptation to the environment.
-Know what we call the ability to pass on a trait (genes) from parents to offspring.
The ability to pass on traits from parents to offspring is called heredity. It’s like when you inherit your parents’ eye color or hair type. This process is controlled by genes, which are segments of DNA that carry the instructions for these traits.
-Individuals produce a lot of offspring. Why? Who leaves more offspring?
Individuals produce a lot of offspring to increase the chances that some will survive to adulthood and reproduce themselves. This is especially important in environments where survival is challenging due to predators, disease, or limited resources.
In terms of who leaves more offspring, it often depeneds on the species and their environment. Generally, individuals that are better adapted to their environment, meaning they have traits that help them survive and reproduce, will leave more offspring. This is a key concept in natural selection, where advantageous traits become more common in a population over time.
-Variation inherently exists in populations. What are two ways we get variation in a population?
What is an adaptation? How is it involved in Darwin’s theory? Know examples of adaptations.
An adaptation is a trait or characteristic that helps an organism survive and reproduce in its environment. These traits can be physical, like the thick fur of a polar bear, or behavioral, like birds migrating to warmer areas during winter.
In Darwin’s theory of evolution by natural selection, adaptations play a crucial role. Darwin proposed that individuals with traits better suited to their environment are more likely to survive and reproduce. Over time, these advantageous traits become more common in the population, leading to evolution.
Examples:
Camouflage: the ability of an animal to blend into its surroundings, like a chameleon changing its color
Mimicry: when one species evolves to resemble another, like the harmless king snake mimicking the venomous coral snake
Beak shape: in finches, different beak shapes are adapted to specific types of food, like seeds or insects
What did Darwin call his theory of evolution? Why do you think he called it this? What is Darwin’s theory of evolution by means of natural selection commonly referred as?
Darwin called his theory of evolution “natural selection”
He used this term because it describes the process by which organisms better adapted to their environment tend to survive and produce more offspring
This idea is similar to the concept of selective breeding, where humans choose which animals or plants to breed based on desired traits. In nature, however, it’s the environment that “selects” which traits are favorable.
Darwin’s theory of evolution by means of natural selection is commonly referred to as “Darwinism”. This term highlights his contribution to the understanding of how species evolve over time through natural processes.
Homologous structures
Similar structures found in more than one species that share a common ancestor
i.e. human arm, bat wing, dolphin flipper, cat foreleg, all have similar internal bone structure
Structures frequently do not have a similar function
Unlikely that several species have similar ancestry if each species evolved independently
Analogous structures
Structures performing similar functions but are not similar in origin, no close common ancestry
i.e. bat wing and butterfly wings
Found in organisms that have similar environmental needs so have similar adaptations using different body parts
NOT evidence for common ancestry
Vestigial structures (organs)
Remnant of structure that may have had important function in species’ ancestors, but has no clear function in the modern species
i.e. human appendix, whale hip-bones, snakes pelvic bones, wings of an ostrich
Takes many generations for the organs/structures to shrink
Scientists consider vestigial structures among most important examples demonstrating how evolution works
Be able to explain what fitness means. Think of some examples.Fitness refers to an organism’s ability to survive and reproduce in its environment. It’s not about how strong or fast an organism is, but rather how well it can pass on its genes to the next generation.
Peppered moths: during the industrial revolution in England, the trees became darkened by soot. Dark-colored moths had higher fitness because they were better camouflaged from predators, allowing them to survive and reproduce more effectively than light-colored moths
Darwin’s Finches: On the galapagos islands, finches with beak shapes that were well suited to their food sources had higher fitness. For example, finches with strong, thick beaks could crack open tough seeds, giving them a survival advantage
Antibiotic resistance in bacteria: Bacteria that have mutations allowing them to survive antibiotic treatment have higher fitness. These bacteria can reproduce and pass on the resistnace genes, leading to populations of resistant bacteria.
Who acts as the selective agent in natural selection?
In natural selection, the environment acts as the selective agent. This means that the environment determines which traits are favorable and which are not, based on how well organisms with those traits can survive and reproduce. For example, if a certain trait helps an organism find food more easily or avoid predators, that trait is more likely to be passed on to future generations.
What does natural selection act on in a population? Are any alleles made in natural selection? Why or why not?
Natural selection acts on the phenotypes of individuals in a population.
Natural selection does not create new alleles. Instead, it acts on existing genetic variation within a population. Alleles are different versions of a gene, and they arise through mutations, which are random changes in the DNA sequence. Once these mutations occur, natural selection can increase or decrease the frequency of these alleles in the population based on how they affect an organism’s ability to survive and reproduce.
In summary, natural selection works with the genetic variation that already exists in a population, favoring alleles that provide a survival or reproductive advantage. It doesn’t create new alleles but can lead to changes in allele frequencies over time.
If a trait is beneficial now, will this always be true? Why or why not?
A trait that is beneficial now might not always be beneficial in the future.
Environmental Changes: The environment can change over time. A trait that helps an organism survive in one environment might not be helpful if the environment changes. For example, a thick fur coat is great for cold climates but not so much if the climate becomes warmer.
Predator and Prey Dynamics: If a trait helps an animal avoid predators, but the predators evolve new hunting strategies, the trait might become less effective.
Competition: If other species or individuals develop new traits that give them an advantage, a previously beneficial trait might become less advantageous
Human influence: Human activities, like urban development or pollution, can change environments rapidly, affecting which traits are beneficial