Exam 1 Flashcards
What different ideas from the idea of special creation did Darwin publish On The Origin of Species by Means of Natural Selection in 1859
- Species are independent
- Life on earth is young
- Species are immutable (incapable of change)
What 2 components are scientific theories comprised of
- Pattern (observations abt natural world)
- Process (mechanism that produce that pattern)
What were Plato’s thoughts
Every organism was an example of a perfect essence, or type, created by God (typological thinking)
What were Aristotle’s thoughts
- Great chain of being
A. Sequence started with minerals and lover plants
B. Humans were at the top of the chain
Species were fixed types as Plato proposed
Some species are higher in the sense of being more complex/better - than others
Lamarck’s ideas on evolution
Suggested that the process responsible for this pattern was the inheritance of acquired characters
Ex: giraffes develop long necks from stretching to reach food and produce offspring with long necks
What are homologous
A similarity that exists in species descended from a common ancestor
The 3 different levels of
1. Genetic
2. Developmental
3. Structural
Genetic homology
A similarity in the DNA nucleotide sequences, RNA nucleotide sequences or amino acid sequences
Developmental homology
Seen in embryos of different species
Ex: tails & gill puches found in the embryos of chickens, humans, and cats
Structural homology
A similarity in adult morphology
Ex: most vertebrates have a common structural plan in the limb bones
Speciation
A process that that results in one species splitting into 2 or more descendant species
Darwin’s 4 postulates
- Variation- Individuals in a population vary in their traits
- Heritability- Some of these differences are heritable; they are passed on to offspring
- Overproduction- In each generation many more offspring are produced than can survive
- Differential survival- Individuals with certain heritable traits are more likely to survive and reproduce
Biological fitness
The ability of an individual ti produce surviving fertile offspring relative ti that ability in other individuals in the population
Biological adaptation
A heritable trait that increases an individual’s fitness in a particular environment relative to individuals lacking that trait
Biological selection
Differential reproduction as a result of heritable variation
Natural selection
Increases the frequency of alleles that contribute to reproductive success in a particular environment
Genetic drift
Causes allele frequencies to change randomly
Gene flow
Occurs when individuals leave one population, join another, and breed
Mutation
Modified allele frequencies by continually introducing new alleles
Natural selection occurs when
Heritable variation leads to differential survival and reproduction
If the favored phenotype is associated with certain alleles
Genetic variation
The number and relative frequency of alleles that are present in a particular population
What variety of patterns or modes does natural selection occur?
- Directional selection
- Stabilizing selection
- Disruptive selection
- Balancing selection
Directional selection
Changes the average phenotype in the population in one direction (tends to reduce the genetic diversity of populations)
Stabilizing selection
Reduces genetic variation in a trait but does not change average value of a trait over time (reduce both extremes in a population)
Disruptive selection
Intermediate phenotypes are selected against and extreme phenotypes are favored (increases variation in trait)
Balancing selection
Occurs when no single allele has a distinct advantage (balance among 7 alleles in terms of their fitness and frequency)
Chromosome level mutations
A change in the number or composition of chromosomes
Lateral gene transfer (horizontal gene transfer)
Transfer of genes from one species to another
Speciation
A splitting event that creates 2 or more distinct species from an ancestral species (can occur gradually or rapidly)
Species
Evolutionary independent population of group of populations
How are species defined and identified
- The biological species concept
- The morphological species (morphospecies) concept
- The phylogenetic species concept
Biological species concept
Main criterion for identifying species is reproductive isolation
(Lack of gene flow)
Prezygotic isolation
Individuals of different species are prevented from mating successfully
Postzygotic isolation
Hybrid offspring do not survive or reproduce
Morphospecies concept
Individual lineages differ in size, shape, or other morphological feature
Species defined by differing morphology
Phylogenetic species concept
A species is defined as the smaller monophyletic group on the tree of life (phylogenetic tree) known as clades or lineage
Subspecies
Populations that
Live in discrete geographic areas
Have distinguishing features
R not distinct enough to be considered a separate species
Can interbreed if geographical barriers are removed
Asexual reproduction
Based on mitosis and occurs without fusion of gametes
Results in offspring that genetically identical to each other and their parent
Sexual reproduction
Based on meiosis and fusion of gametes
Results in offspring that are genetically different from each other and their parents
How does asexual reproduction occur
- Budding - offspring forms within or on the parent
- Fission - an individual splits into two or more descendants
- Parthenogenesis - female produces an offspring without any genetic contribution from the male
Proximate causation
Addresses how a trait is produced
External fertilization
Individuals release their gametes into their environment
Ultimate causation
Address why a trait occurs, in terms of its effect on fitness— the focus is on the evolutionary history of traits
Fertilization
The joining of a sperm and an egg to form a diploid zygote
Internal fertilization
Males deposit sperm into the reproductive tracts of females
Gametogenesis
Occurs in response to environmental cues such as lengthening days and warmer water temperatures (it occurs in a majority of aquatic environments )
Internal fertilization occurs in what ways
- Copulation- males deposit sperm directly into the reproductive tract with the aid of a copulatory organ
- Males make package their sperm into a spermatophore which is then placed into the female’s reproductive tract by the male or female
