Unit 3 BIO 100

What is the difference between bacterial colonization and infection?

Bacterial colonization refers to the presence of bacteria on or within a host without causing disease, while infection occurs when bacteria invade tissues, multiply, and cause harm to the host.

How do beta-lactam antibiotics work?

Beta-lactam antibiotics target and inhibit the synthesis of bacterial cell walls, which leads to cell lysis and death of the bacteria.

What are some examples of beta-lactam antibiotics?

Examples of beta-lactam antibiotics include penicillin, amoxicillin, and cephalosporins.

How does bacteria reproduce?

Bacteria reproduce asexually through a process called binary fission, where one cell divides into two identical daughter cells.

How does bacteria acquire genetic variation?

Bacteria acquire genetic variation through several mechanisms, including horizontal gene transfer, transformation, transduction, and conjugation. These processes allow for the exchange of genetic material between bacterial cells, leading to diversity and adaptation.

Define evolution

Evolution is the process by which populations of organisms change over generations through variations in traits and natural selection. It often results in the adaptation of species to their environment.

Define fitness

Fitness refers to an organism's ability to survive and reproduce in its environment, contributing to the gene pool of the next generation. It is often measured by the number of viable offspring produced.

Define natural selection

Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring. This mechanism drives the evolution of species by favoring the propagation of advantageous traits.

Explain the by process of evolution due to natural selection?

The process of evolution due to natural selection involves variations in traits within a population, where individuals with advantageous traits are more likely to survive and reproduce. Over time, this leads to the increase of these traits in the population, resulting in adaptation to the environment.

Differentiate between direction, stabilizing, and diversifying selection

Differentiating between direction, stabilizing, and diversifying selection involves understanding three patterns of natural selection: directional selection favors extreme traits, stabilizing selection favors average traits, and diversifying selection favors both extreme traits at the expense of average traits.

Define population genetics, gene pool and allele frequencies

Population genetics is the branch of genetics that studies the genetic composition of populations, focusing on how the frequencies of different alleles (gene variants) change over time due to evolutionary forces such as natural selection, genetic drift, mutation, and gene flow. Gene pool refers to the complete set of all alleles for all genes present in a population at a given time. Allele frequency (or gene frequency) is the proportion of a specific allele among all allele copies at a given locus in a population.

Define nonadaptive evolution

Any change in allele frequencies that does not by itself lead a population to become more adapted to its environment; the mechanisms of nonadaptive evolution are mutation, genetic drift, and gene flow.

Define genetic drift and contrast the founder and bottleneck effects

Random changes in the allele frequencies of a population between generations; genetic drift tends to have more dramatic effects in smaller populations than in larger ones. A founder effect occurs when a small group of settlers (“founders”) splits off from a main population and establishes a new one. A bottleneck effect is a type of genetic drift in which a population is suddenly reduced to a small number of individuals, and alleles are lost from the population.

Define gene flow

The movement of alleles from one population to another, which may increase the genetic diversity of a population.

Explain the disadvantages of inbreeding and define inbreeding depression

Because closely related individuals are more likely to share the same alleles, the chance of two recessive harmful alleles coming together during mating is high. When that happens, homozygous recessive genotypes are created in higher frequency in the population, and previously hidden recessive alleles start to affect phenotypes in negative ways. Inbreeding depression is the negative reproductive consequences for a population associated with having a high frequency of homozygous individuals possessing harmful recessive alleles.

Define biological species concept

The definition of a species as a group whose members can interbreed to produce fertile offspring.

Contrast the ecological, behavioral, gametic, temporal, mechanical, hybrid infertility, forms of reproductive isolation.

Ecological, temporal, behavioral, mechanical, and gametic isolation are prezygotic barriers that stop mating or fertilization before a zygote forms. Hybrid infertility and related postzygotic barriers act after fertilization, limiting hybrid survival or reproductive success

Explain how new species form

New species form when populations become genetically and reproductively distinct, whether through geographic separation, partial separation, or ecological/behavioral divergence, with evolutionary forces shaping the process over time

Explain the Urey and Miller “primordial soup” experiment

The hypothesis that life emerged in stages over time, as inorganic chemicals combined into successively more complex molecules, including the ones making up living things. Urey and Miller replicated the chemical environment of the early Earth in a flask, then simulated lightning with electrical sparks. When the contents of the flask were analyzed, organic molecules, including amino acids, were present, formed from reactions between the inorganic precursors. The results suggest one way that life may have started.

Explain descent with modification

Descent with modification is the process by which species inherit traits from their ancestors while accumulating changes over generations, leading to evolutionary diversity.

Describe the evidence for evolution including the fossil record, vertebrate forelimb homology (homologous and analogous structures), embryological similarities, vestigial structures, molecular homology, and biogeography

The fossil record, anatomical homologies, embryology, vestigial structures, molecular data, and biogeography all converge on the same conclusion — that life on Earth has evolved from common ancestors through gradual change and adaptation

Define taxonomy

The identification, naming, and classification of organisms on the basis of shared traits.

List the taxonomic order from broadest to most specific

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

Define phylogeny

The evolutionary history of a group of organisms.

Describe the forces that favor evolution of dark skin

In high‑UV environments, natural selection favored dark skin because it, protects folate and reproductive health, shields sweat glands and skin from UV damage, enables rapid tanning for added protection and matches the intense UV conditions of equatorial Africa

Describe the forces that favor the evolution of light skin

The main forces favoring light skin are selection for efficient vitamin D synthesis in low-UVR environments, reduced UV damage risk in these conditions, and sometimes dietary or cultural changes that lowered vitamin D intake. These pressures became stronger as human populations moved away from the equator or adopted lifestyles with less sunlight exposure

Explain why folate is so important in the body

It is an essential nutrient, necessary for basic cellular processes like DNA replication and cell division.

Describe the problems that arise with low folate levels

can cause severe birth defects such as spina bifida, a condition in which the spinal column does not close, and anencephaly, the absence at birth of all or most of the brain.

Explain how vitamin D is so important in the body

Vitamin D is crucial for good health: it helps the body absorb calcium and deposit it in bones.

Describe the problems that arise with low vitamin D levels

too little might cause bone distortion, and a distorted pelvis would make it difficult for a woman to bear children

Explain what “out of Africa” means

that anatomically modern humans first appeared about 200,000 years ago, in Africa, and spread around the world from there. These modern humans replaced earlier members of the genus Homo, who became extinct as a result. Deciding between these two hypotheses remained controversial until the 1980s, when genetic evidence started to make the picture clear.

Explain how mitochondrial DNA is inherited

we inherit this solely from our mothers

Define hominid

Any living or extinct member of the family Hominidae, the great apes—humans, orangutans, gorillas, chimpanzees, and bonobos.

Give examples of hominids

humans, orangutans, gorillas, chimpanzees, and bonobos.

Explain how long-ago humans evolved from a common hominid ancestor

Modern humans (Homo sapiens) evolved from a common hominid ancestor about 6 million years ago, when the human lineage split from the lineage leading to chimpanzees and bonobos

Which hominid are chimpanzees most closely related to?

most closely related to humans among all living hominids, with bonobos as their other closest living relatives

List and describe the defining characteristics of humans

Humans are characterized by obligate bipedalism, large and complex brains, advanced language, opposable thumbs, rich social structures, and unique cognitive abilities such as self‑awareness, symbolic thought, and theory of mind.

Contrast positive, negative, and neutral selection

Positive selection promotes beneficial mutations, negative (purifying) selection removes harmful mutations, and neutral selection allows mutations to change by chance when they have no fitness effect

Explain the evolution of skin color

Human skin color evolved primarily as an adaptation to ultraviolet (UV) radiation, balancing protection against folate depletion with the need for vitamin D synthesis.