BIO unit 1

What is evolutionary biology?

The scientific study of evolutionary processes that produced the diversity of life on Earth.

What is ecology?

The study of interactions between organisms and the living and nonliving parts of their environment.

How are evolution and ecology related?

They are intimately linked.

What is an observation?

Information gathered by examining or measuring something.

What is a hypothesis?

An explanation based on observations and assumptions that leads to a testable prediction.

What must a scientific hypothesis produce?

A testable prediction.

What is an experiment?

A scientific test carried out under controlled conditions.

What is an independent variable?

The factor the researcher intentionally changes.

What is a dependent variable?

The factor measured to see if it responds to the independent variable.

Scientific method order

Observation → Question → Hypothesis → Prediction → Test → Result.

In a toothbrushing experiment, what could be the independent variable?

Toothbrushing.

In a toothbrushing experiment, what could be the dependent variable?

Number of cavities.

Who said “Nothing in biology makes sense except in the light of evolution”?

Theodosius Dobzhansky.

What determines the distribution and abundance of organisms?

Ecological interactions with living and nonliving components.

What percentage of the BIOL 005C grade is participation?

5%.

What is inheritance?

How traits are passed from parents to offspring.

What is true-breeding?

Producing offspring of the same variety over many generations.

What is the blending model of inheritance?

The incorrect idea that parental genetic material blends together.

Why is blending inheritance incorrect?

It would cause genetic variation to be lost.

What is particulate inheritance?

Parents pass discrete heritable units to offspring.

What are the discrete heritable units of inheritance?

Genes.

Who demonstrated particulate inheritance using pea plants?

Gregor Mendel.

What two scientists' ideas form the Evolutionary Synthesis?

Mendel and Darwin.

What is a chromosome?

An organized package of DNA.

What is a gene?

A region of DNA containing sequences coding for RNA or protein products.

What is a locus?

A specific location on a chromosome.

Are all loci genes?

No.

What is an allele?

A genetic variant occurring at the same locus.

What is genotype?

An organism's genetic makeup or set of alleles.

What is phenotype?

An organism's observable physical and physiological traits.

What does diploid mean?

Having two sets of chromosomes, one from each parent.

What does haploid mean?

Having one set of chromosomes.

What is a gamete?

A reproductive cell with a haploid set of chromosomes.

Examples of gametes

Sperm and egg cells.

What is a zygote?

The diploid cell formed when two gametes unite.

What does homozygous mean?

Having two identical alleles for a gene.

Examples of homozygous genotypes

AA or aa.

What does heterozygous mean?

Having two different alleles for a gene.

Example of a heterozygous genotype

Aa.

What is a dominant allele?

An allele fully expressed in a heterozygote.

What is a recessive allele?

An allele whose phenotypic effect is not seen in a heterozygote.

Does dominant mean more common?

No.

Does recessive mean rare?

No.

What does a Punnett square tell you?

Possible outcomes and probabilities of a genetic cross.

Does a Punnett square give a definite outcome?

No; it gives probabilities.

Tt × tt: probability of Tt offspring

50%.

Tt × tt: probability of tt offspring

50%.

Tt purple × tt white: expected purple offspring

50%.

Aa × Aa genotype ratio

1 AA : 2 Aa : 1 aa.

Aa × Aa probability of heterozygous offspring

50%.

Aa × Aa phenotype ratio under complete dominance

3 dominant : 1 recessive.

What does Mendel's law of segregation state?

Two alleles for a trait separate when gametes form.

When does allele segregation occur?

During gamete formation.

Why did Mendel use garden peas?

Their mating could be controlled and traits had distinct forms.

What did Mendel's F1 hybrids look like?

One of the two parental phenotypes.

Why did Mendel's F1 offspring resemble one parent?

One allele was completely dominant for each character.

What is a dihybrid?

An individual heterozygous at two genes or loci.

What is complete dominance?

The heterozygote and dominant homozygote have the same phenotype.

Example: AA and Aa under complete dominance

They have the same phenotype.

What is incomplete dominance?

The heterozygote has an intermediate phenotype.

Classic example of incomplete dominance

Snapdragon flower color.

Red snapdragon × white snapdragon in incomplete dominance

Pink offspring.

What is codominance?

Both alleles affect the phenotype in separate, distinguishable ways.

Example of codominance

A cow with both white and brown spots.

Incomplete dominance vs. codominance

Incomplete = intermediate; codominance = both traits visibly expressed.

Can dominance depend on how a phenotype is measured?

Yes.

Are all alleles completely dominant or recessive?

No.

What is a polygenic trait?

A trait influenced by multiple genes.

Example of a polygenic trait

Height.

What is pleiotropy?

One gene influences multiple phenotypic traits.

Kappa casein affecting nutrition, antibacterial action, and sedation is what?

Pleiotropy.

What can affect human characters?

Genes, gene interactions, dominance, and the environment.

What is a multifactorial trait?

A trait affected by genes and environmental factors.

What is a qualitative trait?

A trait occurring in distinct categories.

Example of a qualitative human trait

Blood type.

What is a quantitative trait?

A trait showing continuous variation.

Example of a quantitative trait

Height.

What is a pedigree?

A family tree showing inheritance of a trait across generations.

What can pedigrees help determine?

How a genetic trait is inherited through a family.

For a recessive disorder, what genotype is affected?

Homozygous recessive.

What is a carrier of a recessive disorder?

A heterozygous individual who does not show the disorder.

Can two unaffected parents have a child with a recessive disorder?

Yes, if both are carriers.

Aa × Aa: probability of an affected recessive child

25%.

Aa × Aa: probability of an unaffected child

75%.

If a sibling has a recessive disorder and you are unaffected, carrier probability

2/3 ≈ 67%.

Why is carrier probability 67% instead of 50% once you know you're unaffected?

The aa possibility is excluded; 2 of the 3 remaining outcomes are Aa.

What rule is used when a probability question says AND?

Multiplication rule.

Multiplication rule

Multiply probabilities of independent events.

Probability of rolling a 1 AND then a 4

1/6 × 1/6 = 1/36.

What rule is used when a probability question says OR?

Addition rule.

Addition rule

Add probabilities of alternative events.

Probability of drawing a king OR queen

4/52 + 4/52 = 2/13.

Probability rules used in genetics are similar to what?

Coin tosses and dice rolls.

What does a 9:3:3:1 phenotypic ratio suggest?

Two traits assort independently.

A 9:3:3:1 ratio suggests genes are where?

On different chromosomes or very far apart on the same chromosome.

What is a mutation?

A change in DNA sequence.

Why are mutations important for evolution?

They generate genetic variation.

Do mutations occur because organisms need them?

No.

Mutations occur randomly with respect to an organism's needs — True or False?

True.

Does natural selection cause useful mutations to appear?

No.