Exam 3

Bacterial colonization

carry bacteria, not sick.

infection colonization

bacteria enter body and cause illness.

How do beta-lactam antibiotics work?

They weaken bacterial cell walls, causing them to burst under pressure.

Examples of beta-lactam antibiotics:

Penicillin, methicillin, cephalexin – all are beta-lactams.

How is bacteria reproduce?

Bacteria divide by binary fission: one cell splits into two identical ones.

How bacteria acquire genetic variation?

Through DNA mutations during division or by swapping genes (gene transfer).

Evolution

A change in allele frequency in a population over time.

Fitness

Ability to survive and reproduce in a certain environment.

Natural Selection

More survival/reproduction = traits become common in population.

Evolution due to natural selection

Traits that help survival spread through population over time.

Directional

favors one extreme

Stabilizing

favors middle

Diversifying

favors both extremes.

What are 6 ways to prevent/treat antibiotic-resistant infections?

Clean hands/surfaces, take full antibiotics, no antibiotics for viruses, reduce use in livestock, develop vaccines.

Population genetics

allele study

Gene pool

all alleles

Allele frequency

how common an allele is.

Nonadaptive evolution

Random allele change not driven by advantage (e.g., drift, gene flow).

Genetic drift + founder vs bottleneck effect

Drift = random change. Founder = few individuals start new group. Bottleneck = pop. shrinks suddenly.

Gene flow

Alleles move between populations when individuals migrate and reproduce.

Inbreeding + inbreeding depression

Inbreeding raises harmful traits. Inbreeding depression = bad effects from recessive genes showing up.

Biological species concept

Species = can mate & have fertile kids. Different species = reproductively isolated.

Forms of reproductive isolation

Types: ecological, behavioral, temporal, mechanical, gametic, hybrid inviability, hybrid infertility.

How new species form?

Strong barrier splits populations → changes accumulate → become separate species.

Urey and Miller primordial soup experiment

Mixed gases + sparks = amino acids. Life’s building blocks can form naturally.

Descent with modification

All living things are related; differences came from long-term natural selection.

Evidence for evolution (all 6 types)

Fossils show change. Homology in limbs/DNA/embryos. Vestigial parts. Biogeography shows where species spread.

Taxonomy

System to name and classify life based on shared traits.

Taxonomic order (broadest to most specific)

Domain → Supergroup → Kingdom → Phylum → Class → Order → Family → Genus → Species

Phylogeny

Evolution history of species shown in phylogenetic trees.

Forces favoring dark skin

Dark skin protects folate from UV light damage in sunny areas.

Forces favoring light skin

Light skin helps produce vitamin D in low sunlight areas.

Why folate is important?

Folate needed for cell function and development.

Problems with low folate

Low folate = serious birth defects (e.g., spina bifida).

Why vitamin D is important?

Vitamin D helps absorb calcium, supports bones, pregnancy health.

Problems with low vitamin D

Low vitamin D = bone issues, hard childbirth.

Meaning of ‘Out of Africa’

‘Out of Africa’ = all humans came from African ancestors who migrated.

How mitochondrial DNA is inherited

mtDNA comes from mother only, unchanged. Tracks ancestry.

Hominid

Any great ape in Hominidae: humans, chimps, gorillas, etc.

Examples of hominids

Humans, chimpanzees, bonobos, gorillas, orangutans.

How long ago did humans evolve from a common ancestor?

Humans & chimps shared ancestor 7 million years ago.

Closest hominid to chimpanzees

Chimpanzees are most closely related to humans.

Defining characteristics of humans

Walk on two legs, big brain, tools, fire use.

Positive Selection

Treat spreads

Negative selection

Treats shrinks

Neutral selection

No change

Evolution of skin color

Darker skin = better cooling, folate protection. Lighter skin = better vitamin D in low UV.

Why race is an illusion

More genetic difference within skin color groups than between. Race has no biological basis.