BIOL 1620 Module 1

Typological Thinking

Every organism has a perfect essence, essentially unchanging and unrelated

Lamarck

Evolution is progressive, “better” species over time, inheritance of acquired characters

Darwinian Evolution

Chnage in species over time, not linear, variation among individuals in populations

Artificial Selection

Shows the extent of genetic diversity within a single species

Gene

Section of DNA that influences one or more hereditary traits

Genotype

Combination of alleles

Phenotype

observable features

Fitness

The ability of an individual to produce surving, fertile offspring relative to that ability in other individuals in the population.

Adaptation

A heritable trait that increases an individual’s fitness in a particualr enviroment

Darwins Four Postulates

1. Individuals in a population vary in their traits

2. Some of these differences are heritable; they are passed on to offspring

3. In each generation, many more offspring are produced that can survive

4. Individuals with certain heritable traits are more likely so survive and reproduce

Evolution

The change in the allele frequencies of a population over time

Modern Darwin Postulates

1. Heritable variation lead to

2. Differential reproductive success

Evidence of change through time

1. Petrified fossils

2. molds and casts

3. carbon films

4. trace fossils

5. preserved remains

Homology

Descent from a common ancestor

Genetic Homology

a similarity in the DNa nucleotide sequcnes, RNA, or amino acids

Developmental Homology

Seen in embryos of different species

Structural Homology

A similarity in adult morphology

Acclimation

Individuals phenotype changes in repsonse to changes in the enviroment

Adaptation

occurs when allele frequencies ina population change in repsonse to natural selection

Vestigial Trait

A reduced or incompletely developed structure that has no (or reduced) function

Fitness Trade-off

A compromise between traits

Genetic Variation

The number and relative frequecny of alleles that are present in a particular population

Types of Natural Selection

1. Directional Selection

2. Stabalizing Selection

3. Disruptive Selection

4. Balancing Selection

Always increases fiteness

Directional Selection

Chnages the average phenotype in the population in one direction

1. Reduces genetic diveristy

2. Increases Fitness

Positive Selection

Increases the frequecny of an adavantageous alleles

Negative Selection

Decreases the frequency of a deleterious allele

Stabilizing Selection

1. Reduces both extremes in a population

2. Reduces genetic variation

3. Favors intermediate phenotypes

Disruptive Selection

1. Extreme Phenotypes are favored

2. Increases genetic variation

3. Can causes speciation

Balancing Selection

Occurs when no single allele has a distinct advantage

1. allele variation is maintainted

2. Heterozygous Advantage

3. Frequency-dependent selection

Natural Selection

Increase the frequency of alleles that contribute to reprodcutive success in a particular enviroment

Mutation

modifies allele frequencies by continually introducing new alleles

Genetic drift

Any change in allele frequencies in a population due to chance

1. Decreases fitness

2. Prevelant in small populations

Horizonal Gene Transfer

The transfer of genetic material between organisms that are not parent offspring

Central Dogma

DNA-RNA-Protiens

Transcription

The process of using a DNA tremplate to make a complementary RNA

Translation

The process of using the information in mRNA to synthesize proteins

Germ Cell

The reprocuctive cells that produce sperm or eggs

Somatic Cells

nonreproductive cell

Founder Effect

when a group of individuals establishes a new population in a new area

Bottleneck Effect

A sudden decrease in population size

Gene Flow

the movement of alleles between populations

1. reduces genetic variation

Reproduction

replication of DNA and trsnsmission to offspring

Asexual Reproduction

1. Through mitosis

2. Produces clones in which the offpspring are geneticallly identical to one another and to their parent

Sexual Reproduction

1. Occurs through meiosis

2. Produces offspring that are genetically distinct from one another and from their parents

Gametes

Reproductive cells

1. Eggs and sperm

Fertilization

results in a dilpoid zygote

Mitosis

Ploidy doesn’t change

Meiosis

Ploidy is cut in half

Haplontic Life cycle

Gametes - Fertilization - zygote - meisis - spores - mature organism

Alternation of Generations

Gametes - Fertilization - zygote - Multicellular diploid - meiosis - spores - multicellular haploid

Diplontic Life Cyle

Gametes - fertilization - zygote - mature organism - meiosis

2-fold+ cost

Asexual reporduction is much more efficient producing twice as many offspring

+: finding a mate, courtship, cost of meiosis

Why we pay 2-fold+

1. Faster adaptation to changing enviroments

2. Faster reduction of accumulating deleterious mutation

Muller’s Ratchet and Mutational Meltdown

Enough deleterious mutations accumulate that the organism undergoes mutational meltdown

Traits that reduce the 2-fold+ cost of sex

1. Sex swithcing

2. Both asexual and sexual life cyle

3. Increase the parental investment allowing 2-fold increase in offspring #s