Bio 94 Midterm 1 Terms List

Evolution

Change in characteristics of population over time. Species are related to one another and can change through time. Species are a group of living organisms capable of exchanging genes or interbreeding

Population

Group of individuals of the same species. Living in the same area at the same time

Adaptation

Trait that increases fitness of individual in particular environment

Fitness

Ability of individuals to produce offspring.

What two conditions must be met for Natural Selection to occur in a population?

1. Individuals must vary in characteristics that are heritable — can be passed onto offspring

2. In particular environment, certain versions of these heritable traits help individuals reproduce more than other versions

What is the difference between natural selection and evolutionary change?

Natural selection acts on individuals while Evolutionary change occurs in populations

Transitional features

an intermediate trait between older and younger species.

Vestigial traits

Reduced/incompletely developed trait with no/reduced function but similar to ancestral traits. 

Homology

similarity among organisms of different species due to shared ancestry

Hardy-Weinberg Equilibrium

used to determine if a population is evolving. Predict what will happen in the next generation. Develop testable hypotheses about evolution. Estimate frequency of homozygotes & heterozygotes (especially important for studying diseases)

The Modern Synthesis

The application of Mendelian genetics to Darwinian evolution. Mendelian genetics → mating between 2 parents. Hardy Weinberg → allele frequencies in populations.

The gene pool

the total sum of all genes, genetic information, and different gene versions (alleles) held by a single, interbreeding population of a species

Genetic Drift

3 key concepts. It’s random, not adaptive. Small populations are affected

more. May lead to loss (freq = 0) or fixation (freq = 1) of an allele. genetic drift falls and lifts

Gene Flow

individuals leave and join a new population. Gene flow goes to and fro. 

Hardy Weinberg Equilibrium assumes:

1. Large Population

2. No Genetic Drift

3. No Gene Flow

4. Completely random mating

5. No natural selection

6. No mutation

Equation for Hardy Weinberg

p^2+2pq+q^2

Artificial Selection

A kind of non-random mating

Inbreeding

Frequency of homozygotes increases, yet frequency of alleles does not change.

What are three common misconceptions about natural selection?:

Misconception #1) Evolutionary change occurs in organisms

Since whales didn’t use their legs, their offspring didn’t inherit them

Misconception #2) Adaptations occur because organisms want or need them

Bats wanted to fly, so that caused a mutation that led to the wings they needed

Misconception #3) Organisms are optimal because of natural selection

Anteater tongues, which are used for getting ants out of ant nests, are perfect.

Intersexual Selection

Mate choice

Intrasexual Selection

Where individuals of the same sex compete with one another to obtain mates.

Founder Effect

Some individuals leave. Ex: Darwin’s finches

Bottleneck Effect

Big to small population. Disaster, Environmental change, Disease

Point mutations

Change in a single base pair

Chromosomal mutations

Deletion, Inversion, Translocation, Duplication

Lateral gene transfer

movement of genetic material between organisms by any means other than parent-to-offspring reproduction 

Directional selection

a type of natural selection, where an environmental change favors a single extreme physical trait, causing the average trait in a population to shift in that direction over time

Disruptive selection

extreme values for a trait our favored over intermediate values and increases genetic variance split a population into two distinct groups and can lead to a new species

Balancing selection

keeps multiple versions of a gene active in a population in two main ways. This happens when heterozygote advantage and frequency-dependent selection stops any single trait from taking over completely.

Stabilizing Selection

natural selection where the average, middle-of-the-road traits are favored, and extreme variations are selected against

Allopatric speciation

an evolutionary process where new species formed because a group of plants or animals is split by a physical barrier to separate isolated groups

Sympatric speciation

the evolution of a new species from a shared ancestral species while both groups continue to live in the same geographic area

Polyploidy

causes instant speciation a polypoid organism cannot successfully mate and produce fertile offspring with its diploid, parent species

Allopatric speciation by dispersal

occurs when a small group of individuals move to a new distant location and becomes geographically isolated from the main population

Allopatric speciation by vicariance

occurs when a large continuous population of a species is split into two or more separate groups by newly formed physical barrier such as a mountain range a new river or an advancing glacier.

Hybridization fusion

plant or animal cells have their walls removed and are forced to refuse together this month, said bypasses, normal sexual reproduction barriers, allowing a scientist to cross unrelated species

Hybridization reinforcement

evolutionary process where natural selection increases reproductive isolation between two divergent populations. It occurs when interpreting produces hybrid offspring with low fitness or sterility promoting the species to evolve stronger pre-zygotic barriers like meat discrimination to avoid wasting reproductive effort.

Hybrid zones

geographic areas where the ranges of two closely related species or distinct populations overlap, allowing them to interbreed and produce hybrid offspring

What are the three criteria for identifying species?

1. the biological species concept 

2. morphological species concept 

3. three the phylogenetic species concept

prezygotic isolation

mating does not occur. temporal populations are isolated because they breed at different times. Behavioral populations do not interbreed because they have different courtship displays. habitat populations are isolated because they breed in different habitats.

Postzygotic barriers

mating occurs, but no zygotes are produced. Mechanical mating fails because male and female reproductive structures are incompatible. Gametic barrier mating fails because eggs and sperm are incompatible.

Speciation

splitting event that creates two or more distinct species from an ancestral species rapidly or gradually

What are the two steps in speciation?: 

1. Genetic isolation barriers to gene flow isolate two populations within species.

2. Genetic divergence mutation, natural selection and genetic drift occur in each of the isolated populations.

Synapomorphy

is a trait found in two or more taxa that is present in their most recent common ancestor but is missing in more distant ancestors. 

Monophyletic group

is an evolutionary unit that includes an ancestral species and all of its descendants, but no others

Homoplasy

a shared physical or genetic trait in different species that did not come from a common ancestor. Instead, these similar features evolved separately, usually because the species lived in similar environments or faced matching survival pressures.

Parsimony

The first “filtering” method to emerge invoked the principle of parsimony, which assumes that the tree that requires the fewest overall character state changes is hypothesized to be the one that most likely reflects what really happened during evolution.

Evolutionary distance

Evolutionary distance methods begin by quantifying the average frequency of character state changes between individual pairs of taxa, then they search for the tree that best aligns with the total data set.

Maximum likelihood and Bayesian analysis

These mathematical models are more complex than the other methods because they require more information than is provided in the data matrix, such as the probability that in a DNA sequence, a G would be substituted by an A rather than a C or T.

Convergent evolution

is the independent evolution of similar traits in distantly related organisms due to adaptation to similar environments and lifestyles.

Habitat Bias

distortions in data, research, or fossil preservation caused by the preferential sampling, accessibility, or physical characteristics of specific environments over others. It leads scientists to misjudge true biodiversity, population distributions, or ecological trends because certain habitats are heavily favored or ignored

Taxonomic and Tissue Bias

selective skews in the fossil record or biological data where certain types of organisms or body parts are preserved, collected, or studied much more frequently than others, distorting our true picture of biodiversity, ecology, and evolution.

Temporal Bias

occurs when distortions in the physical record or research focus skew our view of the past. Younger sites are often over-represented due to erosion, and recent or modern-era sites are frequently ignored or systematically under-valued.

Abundance Bias

refers to the traditional, flawed tendency of researchers to interpret past human behavior through the lens of constant resource shortage and strict survival limits.

Paleozoic era

lasted from about 538.8 million to 251.9 million years ago. It is the first era of the Phanerozoic Eon. The era began with the Cambrian explosion, which brought a massive rise in complex life, and it ended with the devastating Permian mass extinction

Mesozoic era

lasted from about 252 to 66 million years ago. Known as the "Age of Reptiles" or the "Age of Dinosaurs", it is the middle era of complex earth life. It features three major geological periods: the Triassic, Jurassic, and Cretaceous.

Cenozoic era

Earth's current geological era. It began 66 million years ago after an asteroid wiped out the non-avian dinosaurs. Known as the "Age of Mammals", this era saw mammals, birds, insects, and flowering plants grow dominant, and it continues to the present day

Anthropocene

an unofficial unit of geologic time. It describes a new epoch in Earth's history. In this time, human activity has become the main cause of global environmental, climate, and ecological change.

Adaptive radiation

an evolutionary process where a single ancestral species rapidly diversifies into many new forms. This happens when organisms move to a new environment or when an ecological change opens up empty spaces to live and feed, allowing them to adapt to different food sources and lifestyles.

What Triggered the Cambrian Explosion?

1. Higher oxygen levels               

2. Rise of eukaryotic photosynthesis               

3. The evolution of predation               

4. New niches beget more new niches 

5. New genes, new bodies

Background extinctions

occur when normal environmental change, emerging disease, predation pressure, or competition with other species reduces certain populations to zero.

Mass extinctions

result from extraordinary, sudden, and temporary changes in the environment.

Microbiome

is a community of microbes that naturally inhabits a particular area and encompasses all the genetic material contained within it.

 Microbes

microscopic organisms

 Koch’s postulates

1. Presence: The microbe must be present in every sick organism and absent in healthy ones.

2. Isolation: The microbe must be isolated from the sick host and grown in a pure culture.

3. Inoculation: The cultured microbe must cause the disease when given to a healthy subject.

4. Re-isolation: The same microbe must be taken back out of the new sick subject and shown to be the exact same original organism.

Germ theory of disease

states that infectious diseases are caused by specific microbes in the body—such as bacteria, archaea, and viruses.

Virulence

or the ability to cause disease, is a heritable trait that varies among individuals in a population.

Endospores

are tough, thick-walled, dormant structures formed during times of environmental stress, often in response to a lack of nutrients. 

Enrichment cultures

are based on establishing a specified set of growing conditions—temperature, lighting, substrate, types of available food, and so on. Cells that thrive under the specified conditions increase in numbers enough to be isolated and studied in detail.

Gene transfer occurs in three ways:

1. Transformation—when bacteria or archaea naturally take up DNA from the environment that has been released by cell lysis or secreted 

2. Transduction—when viruses pick up DNA from one prokaryotic cell and transfer it to another cell 

3. Conjugation—when genetic information is transferred by direct cell-to-cell contact 

Bacteria and archaea acquire energy to produce ATP in three ways

1. Phototrophs (“light-feeders”) use light energy to excite electrons. ATP is produced by photophosphorylation.

2.  Chemoorganotrophs (“chemical–carbon-feeders”) oxidize organic molecules with high potential energy, such as sugars. ATP may be produced by cellular respiration—with sugars serving as electron donors—or via fermentation pathways.

3. Chemolithotrophs (“chemical–rock-feeders”) oxidize inorganic molecules with high potential energy, such as ammonia  or hydrogen sulfide . ATP is produced by cellular respiration, and inorganic compounds serve as the electron donor.

Bacteria and archaea fulfill their second nutritional need—obtaining building-block compounds with carbon–carbon bonds—in two ways

1. Autotrophs (“self-feeders”) synthesize their own compounds from simple starting materials such as methane .

2. Heterotrophs (“other-feeders”) absorb ready-to-use organic compounds—called building-block compounds—produced by other organisms in their environment.