Module 4, Section 3

natural selection

a fundamental process in evolutionary biology proposed by Charles Darwin that explains how populations of organisms changes over time, leading to the biodiversity we see today

overproduction, variation, competition, and survival of the fittest

what are the key components of natural selection?

overproduction

organisms produce more offspring than the environment can support

variation

individuals within a population exhibit genetic variation, leading to differences in traits like size, color, and behavior

competition

individuals compete for limited resources, such as food, water, and mates

survival of the fittest

individuals with advantageous traits are more likely to survive and reproduce, passing on their genes to the next generation

adaptation, speciation, and extinction

what are the three main implications of natural selection?

fossils, DNA sequences, homologous structures, vestigial structures, and embryology

what are the types of evidence we have for natural selection?

fossil record

a collection of fossils that provide a window into the history of life on Earth, allowing scientists to study the evolution of species over time

no

is the fossil record complete?

mass extinctions and the evolution of complex life forms

besides evolution, what else does the fossil record provide evidence for?

homologous structures

comparison of the anatomy of organisms to see the presence of common features among vastly different species

vestigial structures

the presence of common but unused structures in organisms that indicates a shared common ancestor that would have once used that trait

Darwin-Wallace theories

natural selection occurs when individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring; overtime, these advantageous traits become more common

reproductive fitness

what idea is central to the theory of evolution?

hardy-weinburg principle

fundamental concept in population genetics that describes the genetic makeup of a population that is not evolving; states that allele and genotype frequencies in a population will remain constant from generation to generation under specific conditions

no mutations, no gene flow, random mating, infinite population size, and no natural selection

what are the conditions of the Hardy-Weinberg principle?

p² + 2pq + q² = 1

what is the formula for the Hardy-Weinberg principle?

the frequency of homozygous dominant individuals

what does p² represent?

the frequency of heterozygous individuals

what does 2pq represent?

the frequency of homozygous recessive individuals

what does q² represent?

mutation

a random change in the DNA that can allow for new or unique traits to arise in a population

genetic drift

occurs when a random or chance event changes the number of individuals in a population (either isolating some individuals or shrinking a population substantially)

pioneer effect, fragmentation effect, or population bottleneck

what effects can come from genetic drift?

pioneer effect

a small number of individuals is isolated and they may be able to mate and reproduce, but will have very little genetic diversity in the resulting population

fragementation effect

a small subpopulation is cut off from the main population by a road or environmental barrier; genetic diversity varies based on population size

population bottleneck

a drastic reduction in population size due to a catastrophic event, such as a natural disaster or disease; loss of genetic diversity due to small population

gene flow

the movement of new genes into a population by migration or emigration of neighboring populations of the same species

migration rate, genetic differences between populations, and population size

gene flow may depend on these factors:

there is genetic variability in a population

why does natural selection occur?

directional, stabilizing, and disruptive

what are the three types of natural selection?

directional selection

when the environment selects for 1 phenotype at the cost of all others

stabilizing selection

when the environment is stable and selects away from any extreme phenotypes, it tends to lead to a more homogenous population

disruptive selection

favors individuals at both extremes of a phenotypic range while disfavoring intermediate phenotypes

nonrandom mating

occurs when individuals chose mates based on specific traits

sexual selection

a type of nonrandom mating that occurs when individuals with certain traits are more likely to mate and produce offspring

reduced or increased gentetic diversity and speciation

what are the effects of geneflow and genetic drift on species diversity?

artificial selection

the intentional breeding of plants or animals to produce offspring with specific desired traits

microevolution

small-scale genetic changes in populations over a short time; genetic drift, gene flow, mutation, and natural selection

macroevolution

large-scale evolutionary changes that occur over long periods of time; origin of species, diversification of groups of organisms, and extinction of species

genetic variation, phenotypic variation, and fitness

what are key factors for adaptation?

environmental pressure leads to genetic variation, which causes differential survivial and reproduction, leading to an increased frequency of adaptive traits

describe the cause and effect relationship of natural selection and how it drive adaptation

speciation

the creation of a new species, one which is genetically dissimilar enough from another that they can no longer breed and produce viable offspring

allopatric speciation, sympatric speciation, and reproductive isolation

through what mechanisms can speciation occur?

allopatric speciation

occurs when populations of the same species are physically separated from each other, often by a geographic barrier

sympatric speciation

occurs when populations of the same species life in the same geographic area, but still become reproductively isolated from each other

polyploidy, disruptive selection, or sexual selection

how can sympatric speciation occur?

reproductive isolation

the barriers that prevent gene flow between two populations

prezygotic barriers

barriers to reproduction prior to fertilization; include differences in mating behavior, physical or temporal separation, or mating rituals

postzygotic barriers

barriers to reproduction after fertilization; include things that hybrid inviability or infertility

lack of genetic diversity

refers to a situation where a population has very little variation in its genetic makeup, often due to a reduction in the size of the population or a lack of gene flow

less adaptability and vulnerability to diseases

what are some consequences of lack of genetic diversity?

increasing gene flow and conservation programs

what are some efforts to address lack of genetic diversity?

taxonomy

the science of naming, describing, and classifying organisms

physical characteristics, genetic similarity, biochemical characteristics, embyological development, and fossil record

what are the criteria for classification?

biological systematics

the study of the diversity of life and the evolutionary relationships between organisms

phylogenetic relationships

the evolutionary relationships between species based on shared characteristics of traits

clade

a group of organisms that share a common ancestor and all of its descendants

synapomorphy

a shared derived character that defines a clade

homology

similarity in structures or sequences due to common ancestry

analogy

similarity in function, but not due to common ancestry (convergent evolution)

respire, move, respond to stimuli, reproduce and grow, and depend on their environment

what do living things do?

binomial nomenclature

what did Carolus Linnaeus create?

taxonomic kingdoms

what did Robert Whittaker propose?

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

what is the taxonomic hierarchy?

bacteria, archaea, and eukarya

what are the three domains of life?

bacteria

what kingdoms are in bacteria?

archaea

what kingdoms are in archaea?

protista, fungi, plantae, and animalia

what kingdoms are in eukarya?

cell type, cell number, mode of nutrition, and cell wall composition

how are organisms classified into their different kingdoms?

multicellular, eukaryotic heterotrophs that ingest food

characteristics of kingdom animalia

multicellular, eukaryotic heterotrophs with cell walls made of cellulose

characteristics of kingdom plantae

eukaryotic heterotrops that absorb nutrients from organic matter

characteristics of kingdom fungi

eukaryotic organisms that don’t fit into other kingdoms

characteristics of kingdom protista

unicellular prokaryotes with unique cell wall composition

characteristics of kingdom archaea

unicellular prokaryotes with diverse metabolic capabilities

characteristics of kingdom bacteria

bionomial nomenclature

a system of naming living organisms using two Latin words to denote the genus and species to which the organisms belongs

eukarya, animalia, chordata, mammalia, primates, hominidae, homo, sapiens

what are the classifications of humans?