1/51
Looks like no tags are added yet.
Name | Mastery | Learn | Test | Matching | Spaced | Call with Kai |
|---|
No analytics yet
Send a link to your students to track their progress
Anagenesis
gradual evolution of a species into a new form without branching. The original species transforms into a new one
Cladogenesis
splitting of a lineage into two or more separate species. It increases biodiversity as new branches form on the tree of life
morphospecies
defined based on physical features like shape, size, and structure, rather than genetic or reproductive data
biological species concept
group of interbreeding organisms that can produce fertile offspring and are reproductively isolated from other such groups
limitations of the biological species concept
Doesn’t apply to asexual organisms (e.g., bacteria).
Not useful for fossils, where reproductive behavior can’t be observed.
Difficult to apply in hybrid zones where gene flow occurs.
Assumes reproductive isolation, which isn’t always clear-cut.
Prezygotic isolation
Prevents fertilization from occurring
Postzygotic isolation
Occurs after fertilization, affecting the viability or fertility of the offspring
Geographic isolation
physical barriers (e.g., mountains, rivers) separate populations
Habitat isolation
Species live in the same area but occupy different habitats
Behavioral isolation
Differences in mating behaviors prevent mating
Temporal isolation
Species breed at different times (day, season, or year)
Mechanical isolation
Incompatible reproductive structures prevent mating
Gametic isolation
Gametes (sperm and egg) are incompatible and cannot fuse
Reduced hybrid viability
Offspring fail to develop properly or die early
Reduced hybrid fertility
Offspring are sterile (e.g., mule)
Hybrid breakdown
First-generation hybrids are fertile, but their offspring are weak or sterile
Adaptive radiation
rapid evolution of multiple species from a common ancestor, often when new habitats or ecological niches become available. Example: Darwin’s finches
Allopatric speciation
when a population is geographically isolated, leading to genetic divergence due to mutation, natural selection, and drift. Over time, the separated populations become distinct species.
Sympatric speciation
occurs without geographic isolation
Polyploidy
causes instant reproductive isolation by doubling the number of chromosomes, making the new polyploid incompatible with the original population
Autopolyploidy
Chromosome duplication within a single species
Allopolyploidy
chromosome duplication that occurs after hybridization between two different species
Gradualism
Evolution occurs slowly and steadily over time
Punctuated equilibrium
Long periods of stability are interrupted by rapid bursts of change, often due to environmental shifts or new niches
hybrid zone
region where two species meet and mate, producing hybrids.
Factors that prevent gene flow include:
Strong selection against hybrids
Ecological differences between parental species
Reinforcement of reproductive barriers
Reduced hybrid viability or fertility
Speciation
the process where one species splits into two or more new species
Microevolution
Small changes in a population’s gene pool over time (like changes in allele frequency)
What characteristics do biologists use to classify organisms into species?
Morphology (body shape & size),
Physiology (body functions),
Biochemistry (chemical makeup)
DNA sequences to classify organisms
Why did Darwin call the origin of species the “mystery of mysteries”?
he was fascinated by how new life forms first appeared on Earth
What is an example of a species unique to the Galápagos Islands?
The Galápagos giant tortoise
What does evolutionary theory try to explain?
How new species form and how populations change over time
Can gene flow occur between different species? Give an example
Yes, like grizzly bears and polar bears producing “grolar bears.”
What determines some phenotypic differences in organisms?
Some phenotypic differences are determined by a single gene pair with clear "either-or" outcomes (e.g., flower color).
What is polygenic variation?
Phenotypic differences that result from the influence of two or more gene pairs and vary along a continuum in a population (e.g., human height).
How is genetic variation measured?
Genetic variation can be measured by gene variability (heterozygosity) and nucleotide variability (DNA sequence differences between individuals).
What is heterozygosity in a population?
Heterozygosity measures the average percentage of gene loci in a population that are heterozygous (have two different alleles)
where does most nucleotide variation occur?
Most nucleotide variation occurs in noncoding regions (introns), which do not affect protein function
What causes non-genetic phenotypic variation?
Non-genetic variation is caused by environmental factors (e.g., diet, climate) and does not lead to evolutionary changes.
What is the only type of variation that has evolutionary consequences?
Genetic variation is the only type that can be passed down to offspring and lead to evolution
What are the sources of genetic variation?
Genetic variation arises through mutation and sexual reproduction (genetic recombination)
How do mutations contribute to genetic variation?
Mutations change the DNA sequence, creating new alleles. Only mutations in gametes (sperm or eggs) are passed on to offspring
What is a point mutation?
A point mutation is a change in a single nucleotide in the DNA sequence, which can create new alleles
What are the possible effects of a point mutation?
can be harmful, beneficial, or have no effect. Harmful mutations can be hidden if recessive, while beneficial mutations are rare.
What three big ideas about life do lepidopterans (like moths and butterflies) illustrate?
1. Adaptation to the environment
2. Unity of life (shared traits)
3. Diversity of life (many species
What was Georges Cuvier’s idea about fossils and rock layers (strata)?
He believed catastrophes wiped out species and new ones came in from other areas (catastrophism).
What idea did Hutton and Lyell propose about how Earth changes?
Changes happen slowly over time through continuous processes (geological gradualism)
What did Lamarck believe about how species evolve?
That traits gained during life could be passed to offspring (use/disuse theory), but this idea is incorrect
Why is Lamarck’s theory of acquired traits not accepted today?
Because acquired traits (like muscle from exercise) are not passed to offspring genetically
What were Darwin’s early studies and career path?
He studied medicine (quit), theology (graduated), and became a naturalist on the HMS Beagle.
What did Darwin observe on his voyage that influenced his thinking?
Fossils similar to living species, species variation by region, and an earthquake showing land changes.
How did an earthquake in Chile affect Darwin’s thinking?
It showed him that Earth’s surface can change gradually, supporting gradualism
What did Darwin notice about animals on the Galápagos Islands?
Each island had different species that likely evolved from South American ancestors