Study flashcards

Stabilising Selection

Gradually selects against deleterious alleles in a stable environment, favoring the optimal phenotype and narrowing the extremes.

Environmental Selection Pressures

Factors within the environment that influence the survivability of a species and drives natural selection.

Natural Selection

organisms with an advantageous phenotype have a selection advantage and pass on their alleles to the next generation, increasing the allele frequency

Directional Selection

Changes to environment change the selection pressures to select more extreme traits over average, neutral traits. The bell curve shifts to the extreme.

Disruptive selection

favors extreme traits for populations due to isolation, leading to two peaks of extreme traits which diverge from one another.

VESIG

Variation, Environment, Selection, Inherit, Generation

adaptive radiation

a species giving rise to new group of organisms comprising of new species, generally after mass extinctions or major changes in the environment.

nonsense mutation

mutation that causes nucleotide substitution to create a stop codon, terminating the translation of that protein.

allele frequencies

the frequencies of alleles will change over time in response to various evolutionary processes.

Natural selection

changes the allele frequencies within a population, favoring ones with better survivability and resulting in fewer diversity of alleles

evolution

the appearance and disappearance of species over time, through natural selection

species

genetically isolated group that is only able to interbreed and produce fertile, viable offspring with other members of that group

Biological species concept

defining species by whether two individuals from different populations can interbreed and produce viable, fertile offspring under natural conditions

morphological species concept

Identifying species based on physical and physiological characteristics

Phylogenetic species concept

identifying species by tracing their dna back to a common ancestor

Disruptive selection

favors extreme traits for populations due to isolation, leading to two peaks of extreme traits which diverge from one another.

VESIG

Variation, Environment, Selection, Inherit, Generation

micro evolution

Changes to the gene pool of a population over time for any reason.

Stabilising selection

Type of natural selection where environment is relatively stable and selective pressures select against deleterious alleles which depart from the optimal phenotype

Directional selection

Type of natural selection where changes in environment lead to selection pressures that select for more extreme traits

speciation

Process by which populations genetically diverge until they are distinct species

Allopatric speciation

Geographic separation of a population from a parent population resulting in the formation of a new species

Sympatric speciation

The divergence of a species from an original species without the presence of a geographical barrier

Isolating mechanisms

Pre and post reproductive mechanisms which prevent a species from interbreeding to produce viable fertile offspring

Galapagos finches

Example of Allopatric speciation different islands with specific environmental niches and a geographical barriers preventing gene flow between finches, leading to speciation

adaptive radiation

Type of macro evolution where a small population giving rise to many new species, generally after mass extinctions or major changes in the environment.

allele frequencies

the frequencies of alleles will change over time in response to various evolutionary processes.

adaptive evolution

unequal chances of reproduction lead to the accumilaton of favorable alleles

Natural selection

changes the allele frequencies within a population, favoring ones with better survivability and resulting in fewer diversity of alleles

Stages of Speciation

1 natural selection favours specific phenotypes to adapt to the environment (microevolution)

2 speciation - population accumilates so many changes they can be identified as seperate species

3 macroevolution - many speciation events result in development of new genera taxa

Taxa

broader classification of a group of many species that have specific traits distinct to other groups of species

Biological species concept

defining species by whether two individuals from different populations can interbreed and produce viable, fertile offspring under natural conditions

morphological species concept

Identifying species based on physical and physiological characteristics

Phylogenetic species concept

identifying species by tracing their dna back to a common ancestor

Pre reproductive isolating mechanisms

Geographic mechanisms, temporal mechanisms, behavioural mechanisms, morphological mechanisms

Post reproductive isolating mechanisms

Gamate mortality, Zygote mortality, hybrid sterility

Geographic isolating mechanisms

Pre reproductive isolating mechanism where populating are separated by geographical boundaries which prevent interbreeding

Temporal isolating mechanisms

Pre reproductive isolating mechanism where populations have different breeding patterns, preventing reproduction

Behavioural isolating mechanisms

Pre reproductive isolating mechanism where populations have different meeting behaviours which are reproductively isolating

Gamate mortality

Post reproductive isolating mechanism where fertilisation between different populations fails due to incompatibility, causing gametes to die before fusion

Zygote mortality

Post reproductive isolating mechanism where fertilisation occurs between populations but genetic incompatibility prevents development and results in zygote death

Hybrid infertility

Post reproductive isolating mechanism where adult offspring is unable to reproduce due to infertility

Homo Sapiens

Species name for modern humans

Taxon

Classification system where organisms are classified in to increasingly specific categories based on their characteristics and ancestry

Primates

Order of mammals characterised by prehensile hands, opposable digits, binocular eyes with 3D colour vision, large cranium and sensitive touch receptors on fingers

Hominids

Superfamily within the order of primates which includes great apes and lesser apes.

Characteristics of Hominoids

• broader rib cage and pelvis

• Molars with 5 cusps

Typically longer arms than legs

Australopithecus

Earliest known Hominin fossil, from which humans evolved

Hominin

Tribe which includes the genus Homo

Adaptations for bipedalism

• Bowl shaped provides

• More centred foramen magnum

• Cranium size

• Carrying angle

• Foot

• Hand

• Spinal curvature

Characteristics of Homonins

• bipedalism

• Smaller canine teeth

• Brow ridge

• S shaped spine

• Foramen magnum

Comparative Anatomy

Determining the relatedness between species based on anatomical similarities.

Embryology

Comparative study of embryos to determine the relationship between their species

Homologous structures

Similar physiological structures shared by different organisms stemming from a common ancestor

Vestigial Homologous structures

A structure in an organism that is no longer useful, indicating that the organism evolved from an ancestor that needed the structure.

Divergent Evolution

Differences between species accumulate and lead to speciation

Analogue Structures

The same key features between organisms that evolved separately due to convergent selection

Convergent Evolution

Unrelated organisms evolving similar adaptations due to similar environments

Molecular Homology

Study of relatedness between species based on their DNA and amino acid sequences from conserved genes

DNA Hybridization

Hybridizing DNA from different species and testing the strength of its connection. the stronger the connection, the more related the species.

Chain Termination Method

Sequencing and comparing DNA, adding dideoxynucleic acids which will terminate the strand if attatched instead of a nucleic acid upon attachment. eventually all combinations can theoretically be made.

Edman Degradation

A chemical attaches to the N terminal amino acid and breaks it off, the amino acid is sequenced. process is repeated for each individual amino acid.

Directional Selection

Changes to environment change the selection pressures to select more extreme traits over average, neutral traits. The bell curve shifts to the extreme.

Genetic Drift

Changes in allele frequencies in a population due to random events that affect genetic diversity

Risks of reduced genetic diversity

Inbreeding - keeps harmful alleles in the gene pool

Lower adaptive potential - vulnerable to new selection pressures due to lack of advantageous alleles

Bottleneck effect

Type of genetic drift where a random event has drastically decreased the population size, leading to loss of unique alleles and less genetic diversity.

Founder effect

Type of genetic drift where a small unrepresentative sample of individuals separate from a larger population and establish a population in a new location, leading to less genetic diversity in the new population.

Gene flow

the introduction or removal of alleles between populations through migration or Interbreeding

speciation

the diverging of a species into different species

Principles of Evolution

adaptive evolution through natural selection

Taxa

broader classification of a group of many species that have specific traits distinct to other groups of species

evolution

the appearance and disappearance of species over time, through natural selection

Fossils

preserved remains and traces of organisms

Mould Fossil

Impression of an organism has been left on the rock, creating a cavity where the organism decayed

Cast fossil

minerals can be fit into the cavity where an impression of an organism was left

petrified fossil

When organic material has been replaced with minerals and rock, most bone fossils are petrified

Trace fossils

Evidence of an organisms activity, more frequent than petrified fossils

Transitional fossils

Rare fossils depicting the intermedeol phase of evolution between an organisms ancestral form and its descendants.

gradualism

The theory that evolution is a steady, gradual divergence of lineages

Punctuated equilibrium

The theory that evolution can be both stable, and rapid if there is a sudden change in environment

fossil dating methods

Absolute dating, Comparative dating methods, stratigraphic correlation, index fossils

Absolute Dating

Assigning a numerical age to the fossil via the physical and chemical properties of the rock

Radiometric Dating

Determines the predictable rate of decay of naturally occurring radioactive isotopes for Absolute dating.

half life

measures time taken for half of the radioactive isotope to decay

Carbon Dating

type of Radioactive dating that measures the decay of carbon-14 into nirtogen-14, accurate for samples up to about 50 000 years old

Comparative Dating Techniques

Determining the age of a rock relative to other similar rocks nearby based mostly on their stratum.

Stratigraphic Correlation

Comparative dating technique that estimates the relative age of a fossil using similar igneous rock

igneous rock

Rock that can be dated with uranium or potassium

index fossils

fossil found used in stratigraphic dating that can be date due to being found in igneous rock. it is easily identifiable and abundant.