chap 10- changes in species over time Flashcards
what is a fossil
any evidence of life from the past
what are the two types of fossil
body fossils and trace fossils
what are body fossils
made from whole or part of an organism
what are trace fossils
rocks that have preserved evidence of biological activity of organisms.
when are fossils likely to form in animals
-when they have hard bones
-when they live near water sources where sediments can be easily deposited on them.
- animals that are rapidly buried
- animals with low chance of disturbance, low oxygen levels and low temp
what are mass extinctions
a collection of fossil animals and plants in a stratum layer giving way abruptly to a completely different collection of fossils in the next stratum due to substantial changes in global environmental conditions.
these sudden changes in global environmental conditions meant that the habitat was no longer suitable for some organisms and they were wiped out
what are index fossils
fossils that are representative of a specific geological time.
what are index fossils used for
dating and correlating the strata in which it is found
what are transitional fossils
fossils that bear features of both an older ancestral life form and a younger descendant.
what do transitional fossils provide evidence for
evolution (can show how a species may have been able to adapt to new conditions)
what is relative dating
looking at the ordering of rock layers and index fossils to determine the relative age of a fossil
what is relative age
the age of an object compared to the age of another object. does not provide exact age of an object
what is absolute dating
assigns a numerical age in years to a fossil or rock
what is the most common form of absolute dating
radiometric dating
what is radiometric dating
based on predictable rates of decay of naturally occuring radioactive isotopes rock or fossil (carbon/potassium/uranium) present in a fossil
what are the 3 isotopes of carbon
carbon-12, carbon-13, carbon-14
what is the half-life of carbon
5730 years
when is carbon-14 radiometric dating thought to be accurate up until
60,000 years
what is evolution
the change in the genetic composition of a population over time
what are mutations
a permanent change in a genetic sequence which can either have a beneficial effect, no effect or a harmful effect on the survival ability of an individual
what are selection pressures
external agents which contribute to selection of variants in alleles that can affect an organisms ability to survive in a given environment
what is a fragmented population
organisms in a population being separated from other groups of the same species
what are isolating mechanisms
refer to the ways in which groups of organisms can become separated for long enough to develop into different species.
what is speciation
formation of a new species
wat is allopatric speciation
divergent evolution of two new species from an ancestral species resulting from separation by a geographical barrier
what is sympatric speciation
when two species evolve from an ancestral population while still inhabiting the same geographical area
what is divergence
a pattern of evolution where groups of organisms become so different from each other that a new species forms
when does divergent evolution occur
when groups from the same species become isolated and different selection pressures work on each isolated population
what is adaptive radiation
a pattern of divergent evolution in which organisms rapidly diversify into many new forms
when does convergent evolution occur
when unrelated organisms evolve similar structures or adaptations to perform a similar function in response to the same selection pressures
what is a species
a group of organisms that can interbreed and produce viable, fertile offspring
what is a subspecies
is a population within a species that show genetic differences across a geographic range. May still be able to interbreed and produce fertile offspring
what are prezygotic isolation mechanisms
1- temporal isolation
2- geographical isolation
3- behavioural isolation
4- sturctural/morphological isolation
5- gamete mortality
6- ecological isolation
what is a hybrid
resultant offspring when sperm of one species fertilises an egg of another species and a zygote forms. generally infertile
what is allopatric speciation
the evolution of a new species that occurs when populations become geographically separated.
causes environmental selection pressures to change the allele frequencies of the two sub populations
when does sympatric speciation occur
when two species evolve from an ancestral population while still inhabiting the same geographical area. there is no geographic isolation, but gene flow is restricted in some other way causing reproductive isolation
what is taxonomy
a naming system that categorises organisms based on hypotheses about evolutionary relationships
what is structural morphology
comparing the development and anatomy of organisms can provide evidence that organisms evolved from a common ancestor
how do homologous structures show evolution
homologous structures evolves from the same ancestral for but have different forms or functions due to different selection pressures
what are vestigial structures
a structure found in organisms that has lost most, if not all of its original function in the course of evolution
what does molecular homology refer to
the similarity of patterns in the nucleotide sequences of polypeptides from different organisms as evidence for a common evolutionary origin.
how can mutations in nucleotide sequences be evidence for evolution
mutations accumulate throughout the genome over time. the more mutations that accumulate in the DNA sequences between two species, the more time will have passed since the two species diverged from their common ancestor
what is phylogeny
the hypothesized evolutionary relationship that exists between species
what are phylogenetic trees
are graphical summary of a proposed phylogeny that are represented as branching diagrams to show the evolutionary relationships between species
what is a taxon
a term used to represent a group of organisms at any hierarchial rank
what does the root represent
the ancestral lineage that gave rise to all of the organisms depicted in the tree.
what does the node represent
the last common ancestor of the organisms whose lineages emerge from it
what is a sister taxa
represents pairs of taxa that are grouped together and are the most closely related taxa on the tree
what is polytomy
nodes that have more than two branches coming off them
when does polytomy occur
when either there isnt enough info to distinguish the order of evolution accurately or when rapid speciation has occured after adaptive radiation in a new environment
what is an outgroup
a distantly related taxon to the group of interest which stems from the base of the phylogenetic tree
what does an outgroup contain
organisms that have the least in common with the rest of the organisms present in the phylogenetic tree
what do phylogenetic trees imply
a passage of time where most ancient lineages branch near the base of the tree and the most recently derived ones branch closer to the tips
what does a cladogram represent
a hypothesis for the evolutionary history leading to the descendant species
what are cladograms characterised by
clades
what are clades
a branch that includes a single common ancestor and all of its descendents
what is a phylogram
a scaled or quantified version of the phylogenetic tree. the branch lengths are proportional to the amount of inferred evolutionary change or the number of nuceoltide changes that have occured during the evolution of the lineage
what is DNA hybridisation
technique that can be used to deyermine the level of similarity between setions of DNA of two species
what does DNA hybridisation involve
the heating of DNA from 2 organisms so that they become single stranded and mixing them to allow the complementary strands of the two organisms to bond when cooled
