Evolution Flashcards
Jean Baptiste de Lemark
THE THEORY OF EVOLTION
Use vs. disuse:
Regularly used organs will be strengthened, organs not used withered away. These characteristics would be passed onto offspring.
disproved by Wessman
Wessman
Discovered germ cells pass information on
disproved Baptiste
Darwin and Wallace
Two independent scientist both come to the conclusion that natural selection was the origin of species.
Voyage of the HMS Beagle
Darwin was ships naturalist, 5 year expedition. Most important observations came from Galápagos Islands.
His hypothesis: beak shapes adapted for eating certain kinds of food. Assumed they originated from same species.
Theory of natural selection
- Overproduction: number of offspring produced is greater than number able to be supported by environment
- Competition: because #1 occurs between same and different species
- Variation: difference in traits among offspring
- Survival of the fittest: favours individuals better able to compete, survive, and reproduce
- Speciation: over generations, new species arise by accumulation of inherited variations
Natural selection
The process by which nature selects the organisms that survive
Adaptation
An inherited trait of set of traits that improve chances of survival and reproduction of organisms
This includes:
Behavioral
Structural
Physiological
Direct evidence of evolution
Fossil evidence:
Can help to establish phylogeny (history of evolution of species) and used to produce phylogenetic trees to explain relationship between species
Types of fossils
- Trace fossils-(indirect)- footprint
- Casts- replica of an organism
- Molds- buried and decays leaving an empty space
- Petrified/permineralized- minerals fill organisms space crystallizing
- Amber or frozen- trapped and hardened
Indirect evidence of evolution
- Embryology*
- Homologous and analogous structures*
- Vestigial structures*
- Physiological evidence*
- Biochemical evidence*
Homeobox genes
A large family of similar genes that direct formation of many body structures during early embryonic development
- found in almost all eukaryotes
- mutations can produce major structural changes causing sudden appearance of new traits in individuals and eventually whole population
Embryology
- embryos from different species are very similar
- theory that similarity is due to common ancestor
Homologous and analogous structures
Homologous: structures in different creatures with similar organization, but different functions, has common ancestor. Evidence of divergent evolution
Analogous: structures have the same function, but have no common ancestor. Evidence of convergent evolution
Vestigial structures
Structures that no longer serve original purpose, but was probably useful to ancestor
Physiological evidence
Shows that wastes excreted by birds and reptiles have same biochemical makeup (uric acid)
Insulin from cows and pigs is almost identical to insulin found in humans
Biochemical evidence
All organisms have same DNA translation table (3 nucleotides code for 1 amino acid)
- DNA comparisons show a great deal of similarity (ex: all organisms have protein called cytochrome C)
Niche and population dynamics
Role of an organism (or population) and how it responds to the distribution of resources, the interaction with competitors for those resources, and the results from experiences and how it is altered.
Competition and population dynamics
When 2 populations attempt to occupy same niche, fierce competition arises. Eventually one population will prove better fitted and drive other out.
Directional selection
Environmental conditions favour individuals at one end of the extremes and curve shifts toward that extreme
Stabilizing selection
Environmental conditions remain stable for long periods at a time. There is selection against extremes.
Disruptive selection
Selection is against the middle of the curve, either extreme is more favourable.
Phenotype
An individuals observable characteristics
Gene pool
All of the alleles (versions) of a populations genes
Allelic frequency
The percentage of a specific allele within a gene pool
Genetic equilibrium
When the frequency of alleles in a population remains the same over a number of generations
A population is not evolving because allelic frequencies remain the same, phenotype does too
Hardy Weinberg principle
Under certain conditions, allele frequencies remain constant from generation to generation
- No natural selection (no alleles are favourable)
- Random mating (not trait makes one individual more likely to mate)
- No migration (new individuals bring new alleles, this can’t happen)
- No significant mutations (also introduces new alleles)
Mutation
Change in individuals DNA due to mutagen (radiation/chemicals)
Most are neutral or harmful, however sometimes result in useful variation and becomes part of gene pool
Recombination
Crossing over results in an unlinking and recombination of parent genes
Genetic drift
An accidental change in gene frequency (ex: fire flood)
Affects smaller populations more
Physical change
Genetic flow
Movement of individuals in and out of the population. This means genes are either lost or new ones are added
Affects smaller populations more significantly
Taxonomy
Field of biology that deals with classifying organisms. Clear communication among scientists requires international system for classifying and naming all organisms
Carolus Linnaeus
Established simple system of groups for naming organisms called TAXA (sing. Taxon). Each taxon is a category into which related organisms are placed based on structural similarities.
Categories go from broadest and most general to smallest and most specific taxa
Modern classification
Kingdom Phylum Class Order Family Genus Species
Scientific name
A binomial system used to identify organism.
- Genus, Species: together makes up organisms scientific name
Classification is based on:
Physical structure: some similarities are easily observable. Internal features may clear up confusion caused by external appearance
Biochemistry: biochemical analysis of DNA and proteins provide newest taxonomic information. More differences between DNA sequence of 2 organisms, more distant common ancestor
Dichotomus key
Took used for identifying unfamiliar organisms. It is a list of observable traits eventually leading to name of organism by comparing two contradicting statements.
Kingdoms
- Monera: all prokaryotes
- Protista: includes unicellular and a few multicellular eukaryotes (2 groups: plantlike and animal-like)
- Fungi: eukaryotic. Fungi have cell walks containing chitin. (Molds, mildews, mushrooms, and yeasts)
- Plantae: multicellular organisms that carry out photosynthesis
- Animalia: most member of the animal kingdom can move from place to place
History on life:
- Earth is 4.5 billion years old
- first life about 3.5 billion years ago
- supported by fossil evidence
First cells
Approx. 3.4 billion years is oldest fossil
- first cells probably absorbed molecules from environment (heterotrophs)
- some adapted to photosynthesis
- others became able to survive in oxygen gas became first aerobic cells
Endosymbiosis theory
Explains origin of eukaryotic cells:
- infoldings of the membranes of prokaryotic cells lead to nucleus ER golgi…
- large prokaryotic cells engulfing smaller ones then living symbiotically with them is how chloroplasts formed
Evidence of endosymbiotic theory
Mitochondria and chloroplasts are about same size as bacteria cells, have double membranes, have limited amount of nucleic acid and ribosomes
DNA functions
- Controls cellular activity: cellular respiration, protein synthesis, and reproduction.
- DNA carries a code. Genetic instructions are encoded in the sequence of bases strung together in DNA
- makes exact copies of itself to pass onto other cells in replication (allows organisms to grow and repair cells) l - Undergoes mutations
- this and recombination of DNA from different sources are reason for life’s diversity
Purines
Have double ring structure: adenine and guanine
Pyramidines
Have a single ring structure: thymine, cytosine, and uracil
DNA to a protein
- DNA codes for amino acid sequence of a protein
- DNA is read by enzyme in nucleus, produce mRNA
- mRNA codes for protein. mRNA is read by ribosome in cytoplasm or on the rER
- 3 base pairs code for 1 amino acid*
DNA and evolution
Different combinations of DNA sequences due to mutations and sexual reproduction explain existence of all the difference species that have lived on earth
Point mutations
A change in a single base pair effecting one amino acid code
Frameshift mutations
A base pair change that effects the whole mRNA after point of mutation
Ex: deletion, duplication, inversion, and translocation
Sexual reproduction advantages and disadvantages
Advantages:
- helps natural selection remove unfavourable mutations from population
- offspring are different than parents increasing variation
Disadvantages:
- happens later
- not always guaranteed
evolution
Process where early forms of life developed and diversified into different forms of life
3 steps in protein production
- DNA codes for amino acid sequence of protein
- Enzyme reads DNA in the nucleus to produce mRNA
- mRNA codes for protein. Is read by ribosome in cytoplasm or rER
Principle and theory
Principle is a judgement or opinion
Theory is a set of ideas used to explain something
Adaptive radiation
Organisms rapidly diversify form ancestral species into new species
