BIOL2150 - Exam 1 (Ch1, Ch 20-23)

The 5 steps of the scientific mehtod

1. Make observations

2. Make predictions

3. Do experiments/ make new observations

4. Gather and interpret data

5. Draw conclusions

cell

The simplest self-reproducing entity that can exist as an independent unit of life

cell membrane

The membrane that surrounds the cytoplasm of the cell, separating the inside of the cell from the outside of the cell; also called the plasma membrane

nucleus

The compartment of the cell that houses the DNA in chromosomes

cytoplasm

The entire contents of the cell enclosed by the cell membrane but outside the nucleus, if present

prokaryotes

An organism in which the cell does not have a nucleus; sometimes used to refer collectively to bacteria and archaea

eukaryotes

An organism with cells that have a nucleus, including animals, plants, fungi, and protists

What are the 3 domains of life?

1. Bacteria

2. Archaea

3. Eukarya

deoxyribonucleic acid (DNA)

The principal molecule of biological heredity; a polymer of nucleotides

ribonucleic acid (RNA)

A molecule chemically related to DNA, synthesized as a complement to its DNA template, and involved in protein synthesis, among other functions

polypeptides (proteins)

The key structural and functional molecule that does the work of the cell, providing structural support and catalyzing chemical reactions

transcription

The synthesis of RNA from a DNA template

translation

Synthesis of a polypeptide chain corresponding to the coding sequence present in a molecule of messenger RNA

What is the central dogma?

The central dogma of molecular biology describes the flow of genetic information. It states that DNA is transcribed into RNA, which is then translated into proteins. This process is fundamental to gene expression and the synthesis of proteins in living organisms.

DNA —> RNA —> proteins

transcription —> translation

nucleus —> cytoplasm/cytosol

DNA replication

The process of duplicating a DNA molecule, during which the parental strands separate and new partner strands are made

mutations

Any heritable change in the genetic material; mutations result from an error in replication or a mutagen, such as radiation or chemicals

metabolism

The chemical reactions occurring within cells that convert one molecule into another and transfer energy in living organisms

adenosine triphosphate (ATP)

A molecule composed of the base adenine, the 5-carbon sugar ribose, and three phosphate groups; provides energy in a form that all cells use to perform the work of the cell

Traits of living things

1. Store and transmit information

2. Separated from the environment

3. Reproduce

4. Harvest energy + metabolism

observation

The act of viewing the world around us

experimentation

A disciplined and controlled way of learning about the world and testing hypotheses in an unbiased manner

hypothesis

A tentative explanation for one or more observations that makes predictions that can be tested by experiments or additional observations

variable

The feature of an experiment that is changed from one group to the next by the researcher

test group

The experimental group that is exposed to a variable in an experiment

control group

The group that is not exposed to the variable in an experiment

scientific inquiry

A deliberate, systematic, careful, and unbiased way of learning about the natural world

theory

A general explanation of a natural phenomenon supported by a large body of experiments and observations

evolution

A change in the genetic makeup of a population over time

natural selection

The process in which, when there is genetic variation in a population of organisms, the variants best suited for growth and reproduction in a given environment contribute disproportionately to future generations (of all the evolutionary mechanisms, the only one that leads to adaptations)

environmental variation

Variation among individuals that is due to differences in the environment

genetic variation

Differences in genotype among individuals in a population

tree of life

An evolutionary tree that shows the evolutionary history and relationships of all extinct and extant (living) organisms

homeostasis

The active regulation and maintenance of a stable internal physiological state in the face of a changing external environment

Fig. 1.7 - Can living organisms arise from nonliving matter?

The presence of maggots in the open jar and the absence of maggots in the covered/sealed jars supported the hypothesis that maggots come from flies.

Redi’s experiment argued against spontaneous generation for insects. 200 years later, Louis Pasteur found that this could be extended to microbes.

Fig. 1.8 - Can microscopic life arise from nonliving matter?

The presence of microbes in the straight neck flask and the absence of microbes in the swan neck flask supported the hypothesis that microbes come from other microbes and are not spontaneously generated.

genotype

Genetic makeup of a cell or organism

Phenotype

Observable characteristics of an organism as determined by the genotype and the environmentm

mutation

A rare variation in the DNA sequence

polymorphism

any genetic difference among individuals that is present in multiple individuals in a population

wild type

The most common allele, genotype, or phenotype present in a population; nonmutant

gene

A unit of heredity, a section of DNA that codes for RNA (not necessarily proteins)

alleles

different forms of a gene

homozygous individuals

…have two copies of the same allele (e.g., aa)

heterozygous individuals

…have two different alleles (e.g.; Aa)

allele frequency

(no. of copies of a specific allele) / (total no. of alleles in population)

stabilizing selection

A form of selection that selects against extremes and therefore maintains the status quo (skinnier, taller bell curve)

directional selection

A form of selection that results in a shift of the mean value of a trait in a population over time (bell curve shifts)

disruptive selection

A form of selection that operates in favor of extremes and against intermediate forms, selecting against the mean (bell curve has a divot)

genetic drift

Random change in allele frequencies from generation to generation

bottleneck

An extreme, usually temporary, (RANDOM) reduction in population size that may result in marked loss of genetic diversity and, in the process, genetic drift

founder effect/event

Acute genetic drift that occurs when only a few individuals establish a new population

nonrandom mating…

only affects genotype frequency (biased by genotype or relatedness)

gene pool

All the alleles present in all individuals in a population or species

Hardy-Weinberg equilibrium

If evolution does not occur, then allele frequencies remain constant.

1. There can be no differences in the survival and reproductive success of individuals.

2. Populations must not be added to or subtracted from by migration.

3. There can be no new mutation.

4. The population must be sufficiently large to prevent sampling errors.

5. Individuals must mate at random.

p + q = 1

p² + 2pq + q² = 1

positive natural selection

Increases the frequency of a favorable allele

negative natural selection

Decreases the frequency of a harmful allele

balancing natural selection

Maintains two or more alleles in a population, at some intermediate frequency (0-100), heterozygous has an advantage

artificial selection

A form of directional selection similar to natural selection, but with selection done intentionally by humans, usually with a specific goal in mind, such as increased milk yield in cattle

sexual selection

A form of selection that promotes traits that increase an individual’s access to reproductive opportunities (from preferences one sex has towards the other)

non-adaptive mechanisms of evolution

• migration = movement of individuals from one population to another (gene flow)

• mutation

• genetic drift = random change in allele frequencies from generation to generation (bottleneck, founder event)

• non-random mating

molecular clock

The observation of rate constancy in molecular evolution: The extent of genetic divergence at a gene in two taxa is thus a reflection of the time since the taxa last shared a common ancestor.

taxon (plural, taxa)

A named taxonomic group at any rank, such as a species, a genus, or a family

speciation

The process whereby new species are produced

biological species concept (BSC)

“Species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups.”

• more useful in theory than in practice

• does not apply to asexual or extinct organisms

• does not account for hybridization

morphospecies concept

The idea that members of the same species usually look like each other more than life other species

• practical, but imperfect

• members of a species may not always look alike (polymorphisms, males v.s. females)

• members of different species may look alike

hybrid offspring

The offspring produced by crossing/interbreeding two closely related species

niche

A complete description of the role a species plays in its environment and of its requirements, both abiotic and biotic

ecological species concept

The concept that there is a one-to-one correspondence between a species and its niche

• a species can sometimes be characterized by its niche

• impossible for two species to coexist in same location in their niches are too similar

phylogenetic species concept

The idea that members of a species all share a common ancestry and a common fate

• “requires that all members of a species be descended from a single common ancestor, but does not specify on what scale this idea should be applied"

prezygotic reproductive isolation

Describes factors that prevent the fertilization of an egg:

• behavioral

• physical

• time (temporal)

• space (ecological, geographic)

postzygotic reproductive isolation

Describes factors that cause the failure of the fertilized egg to develop into a fertile individual:

• hybrid inviability

• hybrid sterility

allopatric speciation

geographic speciation; speciation with no gene flow between diverging populations

• vicariance

• dispersal

vicariance

The process in which a geographic barrier arises within a single population, dividing it into two or more populations that are physically separated from each other

dispersal

The process in which some individuals colonize a distant place far from the parents (large new population)

peripatric speciation

A specific kind of allopatric speciation in which a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately (small new population)

sympatric speciation

speciation with gene flow between diverging populations

instantaneous speciation

speciation that occurs in a single generation

phylogenetic tree

A branching diagram representing a hypothesis about the evolutionary relationships among groups of organisms

synapomorphy

A shared derived character; the basis of cladistic phylogenetic reconstruction

Eight main taxonomic ranks

1. Species

2. Genus

3. Family

4. Order

5. Class

6. Phylum

7. Kingdom

8. Domain

species

A group of individuals that can exchange genetic material through interbreeding to produce fertile offspring

genus (plural, genera)

A group of closely related species

family

A group of closely related genera

order

A rank in taxonomic classification consisting of one or more closely related families (grouped into classes)

class

In the Linnaean system of classification, a group of closely related orders

phylum (plural, phyla)

A group of closely related classes, defined by having a distinct body plan

kingdom

A group of closely related phyla

domain

One of the three largest groups of the tree of life: Eukarya, Bacteria, or Archaea

monophyletic

Describes grouping that include all the descendants of a single common ancestor

paraphyletic

Describes groupings that include some, but not all, of the descendants of a common ancestor

polyphyletic

Describes groupings that do not include the last common ancestor of all members

homology

Characters found in different species that are similar because of descent from a common ancestor

analogy

Describes similar characters that evolved independently in different groups as a result of similar selection pressures

sister group

A group of species that is more closely related to another group of species than to any other group of species

convergent evolution

The independent evolution of similar characteristics in different species —> analogous structures

parsimony

Choosing the simplest hypothesis to account for a given set of observations (opting for the tree requiring the fewest evolutionary steps)

fossils

The remains of once-living organisms preserved through time in sedentary rock

• allow us to calibrate phylogenies in terms of time

• provide a record of extinct species

• place evolutionary events in the context of Earth’s history

trace fossils

tracks, trails, or burrows left by organisms

molecular fossils

DNA, proteins, or lipids left by organisms

radiometric dating

Dating ancient materials using the decay of radioisotopes as a yardstick, including the decay of radioactive carbon-14 to nitrogen for time intervals up to few tens of thousands of years and the decay of radioactive uranium to lead for most of Earth history