Evolution - Chapter 7 Flashcards
Evolution
process that results in biological diversity
slow, continual, unpredictable change
tied to environmental conditions
inexact duplication of genetic information is inevitable
Cause of evolution
genetic mutations provides a means of variation within a species
mutations can be neutral, harmful, or beneficial to a species
advantageous mutations provide a species with an improved ability to survive and reproduce, resulting in a population with a greater tendency towards that mutation
Artificial selection
human influenced reproduction of organisms
the useful species population was increased, and individuals with desirable traits were used to produce subsequent generations
Result of artificial selection
reduced genetic variability
potentially losing valuable genes
increases susceptibility of a species to disease, predators, or detrimental traits
Georges-Louis Leclerc de Buffon
noted organisms that had features that were not useful
theorized that they were previously perfect creations that had changed
Jean-Baptiste Lamarck
although the mechanism he proposed was in error, he is credited for proposing other ideas
evolution is the best explanation for both the fossil record and the extent of diversity of life
earth is ancient
adaptation to the environment is a primary product of evolution
Lamarck’s theory
proposed a mechanism for evolution that included 2 principles
use and disuse = body organs used extensively to cope with the environment became stronger and larger while those that were not used deteriorate
inheritance of acquired characteristics = modifications an organism acquired during its lifetime could be passed along to its offspring
Georges Cuvier
noted that fossils tend to occur in layers, with more complex life nearer the surface
many species do not exist in rock layers above or below them
theory of catastrophism = mass extinctions of species occurred on the planet at intervals, and new, perfect organisms were created to replace them
Charles Lyell
theory of uniformitarianism = geological processes are slow and uniform and have operated from the origin of the Earth to the present
revolutionary, challenged the current beliefs that Earth was very young
James Hutton
theory of gradualism = geological changes are slow and gradual, and take long periods of time
same idea as Lyell, however he did not lead to the conclusion that the Earth is ancient
Reverend Thomas Malthus
wrote essay on social theory that Darwin read
organisms produce more offspring than can be supported, therefore there must be competition among them
Alfred Russel Wallace
young naturalist working in Malaysia
helped Darwin with his discoveries while in the Galapagos Islands
Fossils
traces of organic remains that have been preserved from decay in mineral deposits
initially, fossils were thought to be organisms that lived only thousands of years ago
however, many are very unusual and no fossils of current species are found, some are very deep, and they are often found in unexpected locations
Biogeography
geographical distribution of species
islands have endemic species which are closely related to species on the nearest mainland or neighbouring islands
lands that have similar climates have unrelated animals, indicating that differences in environment are not creating the diversity directly
Comparative embryology and anatomy
closely related organisms go through similar stages of embryonic development
anatomical similarities among species grouped in the same taxonomic category are reflections of their common descent
Homologous features
develop from similar embryological origins
all constructed on the same pattern and include same parts
they therefore share a common ancestor
structures have been modified as they take on new functions
Analogous features
perform the same function as one another, but they are not anatomically similar
indicative of a much more distant relationship and different embryological lines
Vestigial features
structures that serve little to no purpose in an organism, but that are fully functioning in a closely related organism
recall Buffon’s theory
Molecular biology
an organism’s hereditary background is reflected in its genes and their protein structure
two species considered to be closely related by other criteria should have a greater proportion of their DNA and proteins in common than more distantly related species
even taxonomically distant organisms have some proteins in common
Charles Darwin
naturalist who spent many season aboard HMS Beagle
perceived the origin of new species and adaptations as closely related processes
two populations of a species could be isolated in different environments and diverge as each adapted
over many generations, the two populations could become dissimilar enough to be designated separated species
Galapagos Island observations
only plants, birds, insects and reptiles were able to reach remote islands by crossing large expanses of open ocean
many unique species found nowhere else on Earth
unique species are descendants of ancestral species from the nearest continental land masses and will exhibit some similarities
Natural selection
the way in which nature favours the reproductive success of some individuals, leading to evolution over countless generations factors that contributed to this theory = exponential population increase perceived stability of populations limited resources and space struggle for existence uniqueness of individuals individual variation is inherited
Survival of the fittest
an individual’s ability to survive in its environment to reproductive maturity in order to achieve the passing of its genes
this passing of genes results in the adaptation of specied that make them well-suited to their environment
Modern synthesis
paleontologists use radioisotopes which undergo radioactive decay to date rock formations that contain fossils, proving the age of the Earth
Modern theory of evolution
evolution is defined as changes in the gene pool of a species over time
the gene pool consists of all alleles of all the individuals present in a population or particular species
natural selection acts to favour some genetic combinations over others
Mutations
new alleles and genes produced by mutation can give rise to new traits when acted on by selection
homologous genes = closely related species inherit homologous genes which come from a common ancestor
pseudogenes = genes that have mutated so they are no longer useful, they still exist because they were not selected for or against
Modern palaeontology
advances in the understanding of plate tectonics and continental drift have enhanced our understanding of why fossil locations were found in specific areas
