BIO1M03 Week 2

What is a control group?

A specific treatment level that receives no manipulation or a baseline manipulation and serves as a comparison for experimental treatments.

What does controlling for confounding factors mean?

Designing an experiment so variables other than the independent variable do not systematically differ between treatment groups.

What is a confounding factor?

A variable other than the independent variable that differs between groups and could affect the outcome.

What is randomization?

Randomly assigning subjects or experimental units to treatment groups, or randomly assigning treatment order/location, to reduce bias from pre-existing differences.

What is replication?

Using multiple independent experimental groups per treatment so a real treatment effect can be distinguished from chance or individual variation.

Randomization vs. replication

Randomization reduces bias by distributing pre-existing differences; replication provides multiple independent observations to distinguish treatment effects from chance.

Why was the control lure coated in the angler fish experiment?

To ensure that brightness was the only variable that differed between treatments.

Why not leave the control lure completely uncoated?

The coating itself could become a confounding factor because males might respond to the coating rather than brightness.

What is evolution by natural selection?

A process in which populations change over time because individuals with certain heritable traits have greater reproductive success.

Who published On the Origin of Species?

Charles Darwin.

When was On the Origin of Species published?

1859.

What did special creation claim about species?

Species were independent and unrelated, life was only about 6000 years old, and species were immutable.

What is a scientific theory?

A well-supported explanation of a broad class of observations; it is not a guess.

What are the two components of a scientific theory?

Pattern and process.

What is the pattern component of a theory?

Observations about the natural world.

What is the process component of a theory?

The mechanism that produces the observed pattern.

What is typological thinking?

The idea that organisms are examples of fixed, unchanging types or perfect essences.

What did Plato believe about organisms?

Each organism was an example of a perfect essence or type created by God, and types were essentially unchanging.

What was Aristotle's great chain of being?

A linear ordering of organisms based on increasing size and complexity, with humans at the top.

What did Aristotle believe about species?

Species were fixed types organized in a linear hierarchy.

What was Lamarck's theory of evolution?

A progressive theory in which simple organisms moved upward toward larger, more complex forms over time.

What is the inheritance of acquired characters?

Lamarck's idea that changes an individual develops during its lifetime in response to environmental challenges can be passed to offspring.

How did Darwin and Wallace's view differ from Lamarck's?

They proposed that evolution is not necessarily progressive and is based on variation among individuals in populations.

What is a population?

Individuals of the same species living in the same area at the same time.

What is population thinking?

Focusing on variation among individuals within populations rather than viewing species as fixed types.

Why was Darwin and Wallace's theory revolutionary?

It rejected the idea that species are static, replaced typological thinking with population thinking, and proposed a testable mechanism for evolutionary change.

What does natural selection change?

The proportion of individuals with particular heritable traits and the frequencies of the alleles underlying those traits in a population.

Does natural selection make every individual in a population change?

No. Natural selection changes populations, not individual organisms.

What happens to favourable traits under natural selection?

The proportion of individuals with those traits increases over generations.

Does natural selection change an individual's traits during its lifetime?

No. Individuals with favourable heritable traits simply produce more surviving offspring.

What does natural selection do to existing variation?

It sorts existing variants rather than creating the variants itself.

What is an allele?

A version of a gene.

How many copies of most genes does an individual inherit?

Two copies, one from each parent.

What is phenotypic plasticity?

A change in an individual's phenotype in response to environmental changes while the genotype remains unchanged.

Are phenotypic plasticity changes directly passed to offspring?

No, because the individual's alleles have not changed.

What is an example of phenotypic plasticity?

Daphnia can develop protective helmets or spikes when they detect chemical cues from their environment.

What is the difference between phenotypic plasticity and adaptation?

Phenotypic plasticity is an environmentally induced change within an individual, while an adaptation is a heritable trait that increases fitness.

Is evolution goal-directed?

No. Mutations are random and do not occur because organisms need or want a particular trait.

Do organisms evolve traits because they need them?

No. Traits become more common when existing heritable variation is favoured by the environment.

Is evolution progressive?

No. Evolution does not necessarily produce better, larger, or more complex organisms.

Can evolution cause complex traits to be lost?

Yes. Complex traits can be lost or simplified over time.

Does evolution produce a ladder of life?

No. Evolution produces a branching tree of life.

Are there scientifically higher or lower organisms?

No. Organisms have different suites of adaptations rather than being objectively higher or lower.

What is a vestigial trait?

A reduced or incompletely developed structure that has no or reduced function.

What are silent mutations?

DNA sequence changes that do not change the amino acid sequence of the protein.

Why are silent mutations generally not acted on by natural selection?

They do not change the phenotype and therefore generally do not affect fitness.

What is genetic constraint?

A limitation on evolution caused by genetic factors that prevent selection from independently optimizing every trait.

What is genetic correlation?

When selection favouring alleles for one trait causes a correlated change in another trait.

What is pleiotropy?

When a single allele affects multiple traits.

Why can lack of genetic variation constrain evolution?

Natural selection can only act on existing heritable variation.

What is a fitness trade-off?

A compromise in which improving performance in one fitness-related trait or environment comes at the cost of performance in another.

What are examples of fitness trade-offs?

Egg/seed size vs. number of offspring, rapid growth vs. lifespan, and bright colouration vs. attracting predators.

What is a historical constraint?

A limitation on evolution because traits evolve from structures that already existed in ancestors.

Why are adaptations historically constrained?

Natural selection modifies existing structures rather than designing traits from scratch.

What are environmental constraints on evolution?

Limitations caused by changing abiotic and biotic environmental conditions across time or geographic areas.

Why are not all traits adaptive?

Some traits may provide no known fitness benefit or may be constrained by genetic, historical, or environmental factors.

What is descent with modification?

Darwin's description of evolution in which modern species are modified descendants of ancestral species.

What are the two major predictions of the pattern of evolution?

Species change through time, and species are related by common ancestry.

What is a fossil?

A trace or remains of an organism that lived in the past.

What is the fossil record?

The collection of fossils that have been found and described scientifically.

What are sedimentary rocks?

Rocks formed from materials such as sand or mud that are deposited in layers.

Which sedimentary rock layers are usually younger?

Younger layers are deposited on top of older layers.

What is the geologic time scale?

A system dividing Earth's history into eons, eras, periods, and epochs based partly on the fossil record.

What is relative dating?

Determining whether one fossil or rock layer is older or younger than another.

What is radiometric dating?

A method of determining absolute age by measuring the decay of radioactive parent atoms into stable daughter atoms.

What is a parent atom?

A radioactive atom that undergoes decay.

What is a daughter atom?

The stable product formed when a parent atom decays.

How does radiometric dating determine age?

By measuring the ratio of radioactive parent atoms to daughter atoms.

What happens to the amount of parent atoms over time?

It decreases as they decay into daughter atoms.

What is a half-life?

The amount of time required for half of the remaining radioactive parent atoms to decay.

What is the half-life of carbon-14?

Approximately 5,730 years.

How does radiocarbon dating work?

Living organisms absorb carbon-14, but after death they stop absorbing it and the carbon-14 decays into nitrogen-14.

How old is Earth according to radiometric dating?

About 4.6 billion years old.

How old are the earliest signs of life according to the notes?

About 3.4-3.8 billion years old.

What is extinction?

The complete disappearance of a species.

What percentage of species that have ever lived are estimated to be extinct?

Over 99%.

What does the fossil record show about extinction?

Extinction has occurred continuously throughout Earth's history.

What is the law of succession?

The observation that fossil species are often similar to living species found in the same geographic area.

What are transitional features?

Traits in fossil species that are intermediate between ancestral and derived species.

Why are transitional fossils evidence for evolution?

They show intermediate forms predicted if traits in newer species evolved from traits in older species.

What is an example of a transitional sequence?

The gradual change from an aquatic fin to a terrestrial limb.

Why are vestigial traits evidence for evolution?

They are remnants of structures that were functional in ancestors and show that species have changed through time.

What are examples of evolution observed today?

Bacteria evolving drug resistance, insects evolving pesticide resistance, weeds evolving herbicide resistance, and changes in migration or flowering in response to climate change.

What does evolution predict about species?

Species are not static; they change through time.

What does evolution predict about the relationships among species?

Species are related through common ancestry.

What did Darwin observe about Galápagos mockingbirds?

Mockingbirds on different islands were similar overall but differed between islands.

What did Darwin propose about Galápagos mockingbirds?

They were similar because they descended from a common ancestor.

What is a phylogenetic tree?

A diagram representing evolutionary relationships and common ancestry.

What did DNA analyses show about Galápagos mockingbirds?

The different species are each other's closest living relatives and share a common ancestor.

What is homology?

A similarity among species that exists because they descended from a common ancestor.

What are the three levels of homology?

Genetic, developmental, and structural.

What is genetic homology?

Similarity in DNA, RNA, or amino acid sequences between species.

What is developmental homology?

Similarity in embryonic structures or developmental processes among species.

What is structural homology?

Similarity in adult anatomical structures among species.

What is an example of developmental homology?

Tails and gill pouches occur in the embryos of chickens, humans, and cats.

What is an example of structural homology?

The similar arrangement of limb bones among vertebrates.

Why do homologous structures exist?

They were inherited from common ancestors.

How can genetic homology produce developmental homology?

Shared genetic information can produce similar developmental structures in related species.

Why can homologous proteins be useful in medical research?

Drugs can be tested in model organisms when the proteins or gene products they target are homologous to those in humans.

What is internal consistency?

The observation that independent sources of data agree in supporting predictions made by a theory.