Download History of Life on Earth Vocabulary

History of Life on Earth Vocabulary
Theory – in science, an explanation for natural events that is based on a large number of observations and is
in accord with existing scientific principles
Uniformitarianism - The hypothesis that Earth developed gradually through natural processes still at work
today occurring over long periods of time. For Example we see limestone forming in shallow sea water
from the shells and tests of living organisms, Limestone on top of the Sandia Mountains was formed in the
same way.
Stratigraphy - a branch of geology, studying rock layers and layering (stratification). It is primarily used in
the study of sedimentary and layered volcanic rocks. The premise is that the youngest layers are found on
top and the older layers are found on the bottom because the piled up as they formed (If nothing happened
to disturb these layers.) Can be used for relative dating of the rock layers and fossils found with in the
layers.
Extinction – the death of all members of a species. Or the death of the last individual of a species.
Fossil – The remains of an organism or sign of an organism, usually preserved in rock. Fossils include
mineralized wood, shells, bones, impression or casts of bodies or body parts including leaves, feathers or
foot prints.
Plate tectonics - is a theory of geology that has been developed to explain the observed evidence for large
scale motions of the Earth's lithosphere. According to the theory, the surface of the Earth is broken into
large plates. The size and position of these plates change over time. The edges of these plates, where they
move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and
mountain building. Plate tectonics is a combination of two earlier ideas, continental drift and sea-floor
spreading. Continental drift is the movement of continents over the Earth's surface and in their change in
position relative to each other. Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges
and movement of the crust away from the mid-ocean ridges.
Paleontology - the study of prehistoric life forms on Earth through the examination of plant and animal
fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilized feces
(coprolites), and chemical residues.
Geologic Time Scale - used by geologists and other scientists to describe the timing and relationships
between events that have occurred during the history of Earth.
Radiometric dating - is a technique used to date materials, based on a comparison between the observed
abundance of particular naturally occurring radioactive isotopes and their known decay rates. It is the
principal source of information about the absolute age of rocks and other geological features, including the
age of the Earth itself. Among the best-known techniques are potassium-argon dating and uranium-lead
dating. Radiocarbon dating is used on fossils and other organic matter that is less than 500,000 years old.
Fitness – the reproductive success of an organism usually expressed in relation to the average reproductive
success of all individuals in the same population.
Founder effect – a type of genetic drift in which an isolated population founded by a small number of
individuals may develop a gene frequency that are very different from the parent population because of
chance.
Artificial Selection – is the intentional breeding for certain traits, or combinations of traits, over others.
Also known as selective breeding. Has allowed breeders of plants and domesticated animals to develop
different breeds with desired traits.
Hardy-Weinberg principle - - is a relationship between the frequencies of alleles and the genotype of a
population. Hardy, Weinberg, and the population geneticists who followed them came to
understand that evolution will not occur in a population if seven conditions are met:
1. mutation is not occurring
2. natural selection is not occurring
3. the population is infinitely large
4. all members of the population breed
5. all mating is totally random
6. everyone produces the same number of offspring
7. there is no migration in or out of the population
Endosymbiosis – A hypothesis stating that certain organelles especially chloroplasts and mitochondria were
bacteria captured inside of another cell and they developed a mutually symbiotic relationship resulting in
the eukaryotic cell. One piece of evidence that supports this theory is that chloroplasts and mitochondria
have their own DNA.
Antibiotic resistance – the ability of a mutated bacteria, fungus or parasite to resist the effects of an
antibiotic that normally kills it.
Antibiotic – a drug or chemical compound that kills or prevents the growth of bacteria, fungus or parasites.
Adaptation – Characteristic of an organism that helps it survive in a particular environment. Also the
process of acquiring useful characteristics.
Natural selection – the unequal survival and reproduction of organisms due to the environment, resulting in
preservation of favorable adaptations. Based on the differential survival and reproduction based on genetic
differences among individuals.
Homologous structure – Structures that differ in function but have similar anatomy, presumably because of
descent from a common ancestor.
Analogous structure – Structures that have similar functions and superficially similar appearance but very
different anatomy, such as the wings of incests and birds. The similarities are due to similar selective
pressure rather than common ancestry.
Vestigial structure – Structures that serve no apparent purpose, but which are homologous to functional
structures in related organisms. Provides evidence for evolution.
Embryological development – the development of an embryo whether in an egg sac as in fish, birds and
reptiles or in the womb of mammals. All vertebrates show many similar stages of development and share
homologous structures. In early stages of embryological development many species of vertebrates look
similar.
Gene pool – the total of all alleles of all genes in the population; for a single gene the total of all the alleles
of that gene that occur in a population.
Allele frequency – frequency of a certain allele in a population of breeding organisms.
Genetic equilibrium - a hypothetical state in which a population is not evolving because the allele
frequencies remain constant over time. This can be due to stabilizing selection selecting against the
heterozygotes.
Genetic drift – a change in the allele frequencies of a small population purely by chance.
Stabilizing selection - The individuals that survive and reproduce more successfully are those that have
intermediate phenotypic values. Put another way, extreme values of the character are selected against.
Mortality among newborn infants, for example, is highest when they are either very small or very large;
infants of intermediate size have a greater chance of surviving.
Directional selection – Type of selective pressure favoring one end of a range of variation in a particular
trait. For example on the Galapagos Islands when there is a drought and only large seeds with tough seed
coats are left, the Darwin’s finches with the largest beaks survived better.
Disruptive selection – Type of selection favoring the two ends of the range of variation for a particular trait.
Organisms with the Intermediate or “Middle of the Range” trait are selected against. Disruptive pressure
can lead to speciation.
Population – group of individuals of the same species, found in the same time and place and are able to
interbreed.
Speciation – a process resulting in new species when two population are reproductively isolated and are no
longer able to breed because of physical, genetic or behavioral differences.
Geographic isolation – When two populations of the same species are separated by a geographic barrier
such as a mountain range, a wide river or an ocean. Some physical barrier prevents the two populations
from interbreeding. This may lead to divergence of the two populations into different species.
Reproductive isolation – any barrier that prevents two different species from successfully interbreeding.
Temporal barriers are when the organisms breed at different times, Barriers may be behavioral, mechanical
or chemical incompatibility. If an offspring is produced it is called a hybrid and hybrids are often sterile
due to genetic incompatibilities.
Polyploid – Having more than two sets of Chromosomes.
Gradualism – a model of evolution, stating that morphological change and speciation are slow, gradual
processes that are not necessarily simultaneous or linked.
Punctuated equilibrium – model of evolution stating the morphological change are rapid, simultaneous
events separated by long periods during which the species remains unchaged.
Evolution – Descent with modification. Decent of different species from a common ancestor through
inheritance of genetic traits. . Changes in the gene frequencies in populations of an organisms that can
eventually result in the development of new species.
Coevolution – The evolution of adaptations in two species due to their extensive interactions with each
other, so that each species acts as a major force of selection on the other species. One example of this is the
yucca and the moth that pollinates it. Yucca flowers are a certain shape so only that tiny moth can pollinate
them. The moths lay their eggs in the yucca flowers and the larvae (caterpillars) live in the developing
ovary and eat yucca seeds.
Adaptive radiation – the rise of many new species in a relatively short time as a result of a single species
invading new habitats and evolving under different selective pressures in those habitats, or adapting to fill
different niches within those habitats, as with Darwin’s Finches.
Divergent evolution – when a single species splits to form two or more new species that exist at the same
time.
Convergent evolution –the independent evolution of similar structures among unrelated organisms, due to
similar selective pressures, creates analogous structures