Terms in this set (75)
words derived from the same common ancestor
Cognates are recognized by having related meanings and similar sounds
apply phylogenetic methods (developed to infer historical relationships among species of organisms) to studying cultural creations such as languages
change in the genetic composition of a population over time
Is all evolution is due to natural selection?
not all evolution is due to natural selection (but all adaptation is)
our understanding of how evolutionary change occurs and what evolutionary changes have occurred in the past
groups nested within groups - Linnaeus (1730s) - used nested pattern -> classification (spp., genera, orders, classes, kingdoms)
Jean-Baptiste Lamarck (1809)
species change - Jean-Baptiste Lamarck (1809) first to propose a clear theory of evolution • incorporated as core mechanism the existing idea of inheritance of acquired characteristics, now closely associated with Lamarck ("Lamarckism")
Georges Cuvier (1769-1832)
- Father of Paleontology - Convinced of extinction, but did not believe in evolution of species • believed less perfect species were wiped out by catastrophes so better ones could be created
Charles Lyell (1797-1875)
All of Earth's geological features can be explained by processes that still occur today - Wind, water, earthquakes, volcanism - but all take a long time - Earth must be truly ancient!
Darwin, Wallace (1850s)
species are related by shared ancestry
species can split into separate species & diverge • "descent with modification" • twigs on a "tree"
wild populations can evolve by natural selection
Animal & plant breeding:
Evolution by natural selection
If not all individuals can survive and reproduce (which must often be the case) AND • If individuals vary in their traits AND • If these traits affect their survival or reproduction AND • If "successful" traits are inherited (somehow), THEN The frequency in the population of successful traits (and successful alleles) will increase: the population will evolve!
Adaptation - and a word of caution...
natural selection leads to adaptation ... but not all useful features are adaptations for that use!
Pattern & Process
pattern - species are not constant - species related by common ancestry • process - natural selection
major lines of evidence: for evolution
extinction • transitional forms • direct observation
establishes extinction (~1810) - Irish elk; mammoths • Irish elk extinct ~11,000 BP, mammoths a bit later - convinced biologists: extinction happens!
"law of succession"
fossils in a location closely resemble living species in that location
eventual explanation: • extinct & extant forms related • fossils = ancestors!
drug resistance in bacteria • pesticide & herbicide resistance in agricultural pests • herbivore change following plant introductions • artificial selection
Transgenic corn engineering with genes expressing insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) is now a major tool in insect pest management
Species are related by common ancestry major lines of evidence:
biogeography • homology
related species on neighboring islands
cave organisms - closest relatives typically nearby non-cave organisms (not cave dwellers elsewhere)
similarity resulting from shared ancestry - structural homology
The Fundamental Insights Into Natural Selection
Variation - observable, but previously underappreciated 2. Heritable variation - phenomenon known, but not mechanism 3. Struggle - influence of (Thomas) Robert Malthus: populations will outgrow their resources, so not all individuals can survive 4. Differential reproduction based on heritable variation - some genetic variants will leave more descendants in future generations
if 1-4 hold, then the population's heritable characteristics will change = evolution by natural selection! (assuming random factors don't interfere)
proportion of trait variation in a population accounted for by genetic variation in the population - a ratio, with value ranging from 0 to 1 • 0 - trait variation entirely determined by environmental variation • 1 - trait variation entirely determined by genetic variation
4 processes lead to evolution
natural selection • leads to adaptation - mutation - migration (gene flow) - genetic drift
height variation in a population if every time a larger individual and a smaller individual reproduced, their offspring were intermediate in size - problem: destroys variation!
hereditary determinants remain intact across generations - 1850s/1860s
discrete unit of information coded by DNA (or RNA)
genes are on chromosomes (long DNA molecules)
the two strands formed when a chromosome duplicates itself as part of the early stages of cell division
location of the gene on the chromosome
# chromosome types - varies among species
diploid (2n) cell
2 copies of each chromosome - homologous pairs of chromosomes - one from Mom and one from Dad
haploid (1n) cell
1 copy of each chromosome - each chromosome from either Mom OR Dad
alternate forms of a gene
2 copies of same allele -
2 different alleles
genetic make-up of organism
discernible features of organism
an observable feature of an organism (e.g., eye color)
specific form of a character (e.g. blue vs. brown eyes)
Mendel's Principle of Segregation emerges from meiosis
During gamete formation, the two alleles present for a particular heritable character separate, with just one ending up in each gamete
following one trait
cross between 2 heterozygotes
fully expressed in the phenotype
not expressed in the phenotype
cross individual with unknown genotype with a homozy
Principle of Independent Assortment
genes for different traits can segregate independently during the formation of gametes because they are on different chromosomes or far apart on the same one
For human (n=23) making gametes, ~8.4 million possible combinations of maternally & paternally sourced chromosomes!!!
Mendel's Principle of Segregation
allele pairs at a locus separate during gamete formation, and randomly unite at fertilization
Mendel's Principle of Independent Assortment
- allele pairs on different chromosomes separate independently during the formation of gametes
crossing over during meiosis I (even more combinations)
if close together on same chromosome - inherited together
phenotype of Aa = AA
Aa phenotype intermediate between aa and AA
heterozygotes have dual phenotype, associated with both alleles - e.g., blood membrane proteins • MN blood gene • ABO blood gene
occurs when single gene influences more than one phenotypic trait
effect of allele at a locus depends on what alleles are present at other loci
qualitatively different; like categories
vary in gradations along a continuum (height, weight, skin color
influenced by many genes
proportion of individuals in a group with genotype X that actually exhibit an expected phenotype - e.g., women with certain mutations of BRCA1 gene are much more likely to develop breast cancer • but many don't (presumably due to other genetic and/or environmental factors), so this mutation exhibits "incomplete penetrance"
degree to which a genotype is expressed in an individual - e.g., one woman with BRCA1 mutation may develop both breast & ovarian cancer, while another develops only breast cancer, so this mutation shows "variable expressivity
natural selection can favor different parts of a phenotypic distribution
favors individuals with trait values near mean • average trait value stable, but variation reduced
favors individuals at one end of distribution • increases or decreases average trait value
favors individuals with extreme trait values; disfavors middle phenotypes • variation increases • average trait value can stay same • can facilitate speciation
random change in allele frequency - random with respect to fitness • can be powerful force • most pronounced in small populations
prominent when: 1) new population established by small # of individuals 2) population size dramatically reduced = population (genetic) bottleneck
allele becomes the only allele in the population
change in allele frequencies when new population established
population (genetic) bottleneck
population size dramatically reduced =
What are some circumstances that will increase relative importance of drift in determining outcome?
small population size - fitness difference between alleles small (weak selection) • incl. selection on nearby regions of chromosome
What are some circumstances that will increase relative importance of selection in determining outcome?
large population size - fitness difference between alleles large (strong selection) • incl. selection on nearby regions of chromosome
movement of alleles from one population to another - individuals or gametes • "migration"
homogenizes allele frequencies of different populations
change in heritable material (DNA) - introduced as "errors", e.g., • errors in synthesis or repair • errors due to damage (X-rays; chemicals) • unequal crossing over (duplication/deletion) • chromosomal translocation - nonhomologous chromosomes swapping pieces • errors in chromosome segregation - abnormal chromosome complement in daughter cells in meiosis or mitosis
the more tightly linked DNA is to selected allele, the more it increases in frequency along with selected allele
OTHER SETS BY THIS CREATOR
Cell extra credit
Word list #10 - Coral and Sapir