Bio Test #1

Trait Values

quantifiable expression status of a particular feature of a organism

Phenotype

all the observable characteristics of the organism including behavior, morphology, and physiology

Genotype

Set of genes or gene variants (alleles) that an organism carries

Morphological Trait

Coloration

Behavioral Trait

Degree of social dominance

Physiological Trait

example: Red Blood Cells

Genetic Trait

DNA sequence

Fitness

lifetime reproductive output of an individual (# offspring) relative to the population average

Charles Darwin’s 3 Components of Evolutionary Process

1.) Species change over time

2.) Divergent species share a common ancestor and diverged gradually over time: descent with modification

3.) Changes in species over time explained by natural selection (ie. increased reproductive success (fitness) of some individuals compared to others because of differences in their traits (= trait value)

Evolution

Change in the proportions of heritable traits of populations of organisms over the course of generations

1+3 Forces of Evolutionary Process

1.) Mutations (prerequisite force)

2.) Gene Flow 3.) Genetic Drift. 4) Selection

Moss

• 12,000 species

• Existed as early as the Permian period

• Absorbs water and nutrients through leaves

• Harvest CO2 and sunlight for photosynthesis

• Important for soil-atmosphere interfaces with regard to water exchange

• Not all moss species absorb H2O at some rate

Moss Threats

• Habitat loss ——> deforestation

• Habitat degradation ——> Pollution

• Climate Change ——> Change in raining

Physiology

The how physical structures in an organism function; study of the physical and chemical processes associated with life

Conservation Biology

addresses the biology of species, communities, and ecosystems

DNA

• Genetic material

• encodes info as large as macromolecules as a long sequence of 4 nucleotides

  • Adenine (A), Guanine (G) [Purines]

  • Thymine (T), Cytosine (C) [Pyrimidines]

• Very Stable

Chromosomes

• # of chromosomes in a cells nucleus is constant within a species and often different among species

• Somatic Cells contain 2 sets of chromosomes; one set from mother, one set from father——> diploid (2n)

• Gametic Cells (egg, sperm) contain 1 set ——> haploid (n)

Genes

• Each gene has several thousand nucleotides and tells a cell how to make a particular protein

• Bodies are made out of proteins

• DNA = set of instructions on how to make certain proteins at certain times and certain places to thus the organism

• The DNA sequence for a given gene can differ slightly among chromosomes and individuals

Variants —→ Alleles

One of two (or more) versions of a previous mutation at the same place (locus) on a chromosome

Allelic Veration

The basis for genetic differences among individuals in a population

• Heterozygous (2 diff versions)

• Homozygous (2 same versions)

Structure of Genes

• Begins with Start codon and ends with stop codon

• In between are the DNA sequences that code for a protein (exon) interrupted by introns (noncoding DNA) Exons are then spliced together

• DNA → RNA → Proteins

• Proteins are sequences of amino acids each amino acid is specified by a sequences of 3 nucleotides (codons)

• Info is flowing from genotype to phenotype

Cell Division

• DNA replicates

• Each daughter cell gets a complete copy

• DNA replication is very precise

• Mistakes = mutations

Replication mechanics

Enzymatic machinery loosens the 2 strands of the helix and forming a new copy on each of the two liberated strands

Mitosis

2 daughter cells each get a complete set of chromosomes (identical somatic cells)

Meiosis

Produces haploid gametes from diploid cells (germ line cells)

Law of segregation

Predicting offspring genotype ratios when 2 heterozygotes mate

• If there are two alleles at a locus, the probability that one of them will get into a given gamete is exactly 50%

Dominant

See in the heterozygote phenotype that the allele is present

Recessive

Cannot see in the heterozygote phenotype that the allele is present

Law of Independent Assortment

Genes on different chromosomes assort independently at meiosis

Crossing over

Generates genetic diversity through new allele combinations (meiosis 1)

Recombination

Meiosis produces gamete genotypes that differ from the parental genotype in the combination of alleles

Types of Mutation and their implications

• Mitotic errors→ possible cancer

• Meiotic errors → germline affected → evolutionary implications

• Deleterious → result in worse protein function

• Neutral → No effect on protein

• Beneficial → Improved protein function

Point mutations

addition, deletion, or substitution of 1 or a few nucleotides pairs

Synonymous Mutations

Not all gene changes affect the amino acid sequence

Chromosomal Mutations

• Gene duplications

  • use old copy to keep things working while you innovate with the new copy

• Inversion

  • loop to a straight line

Gene Flow

The transfer of traits (via alleles) from one population to another. It occurs when organisms or their gametes disperse from one population to another

Evolution by Immigration Example

• Band and unbanded water snakes in Lake Erie

• mainland→ banded(mainly) → vegetated shoreline

• Island→ unbanded(mainly) → hide better on the stone

• Banded snakes experience predation on island and vice versa

• Big concept: “adaptiveness” of trait is not an intrinsic property of the trait itself but rather the relationship between trait and its environment

Genetic Drift (Neutral Evolution)

Random fluctuations in trait (allele) frequencies from one generation to the next. Most important in small populations

• Population Bottlenecks & Founder Effects

• Fairness of meiosis & mendelian lottery

Bottlenecks

Passage through small population sizes

Fixation

Every organism ends up with the same trait even though there are no effects of these alleles on reproductive success

Genetic Drift

Can cause random fixations of alleles and loss of heterozygousity

• No selection based on trait values at work here

  • random act of bad luck

  • traits can fluctuate widely in small populations

Founder Effect

Same concept as bottleneck but just due to a few founders

• A few individuals found a new population and bring them with them only a small proportion of the genetic variation of the original stock

Mendelian Lottery

Neutral alleles can just end up in vessels (organisms) that have low/high reproductive success unrelated to that particular gene

• end result is a kind of Brownian motion of allele frequency over time

Selection

yields adaptations

Adaptive Evolution

Traits that have changed such that they cause their bearers to have higher fitness by making the organism better suited to survive & reproduce in its environment

Evolution by Selection Requirements

1.) Variation in reproductive success among individuals in population

2.) Variation in some trait (ex. differing trait values)

3.) Trait has significant heritability

4.) Correlation between reproductive success and this trait

Natural Selection

Any consistent difference in fitness among phenotypically different individuals

• ex. Some individuals survival/reproduce more than others because of their traits

Evolution by Natural Selection

• If that trait was heritable

• If generation(s) have passed

• Then proportion of trait values in offspring population will be different

Polygenic

Complex continuous trait

Breeders Equation

R = h² x S

• S = strength of selection

  • equal to the difference in mean trait values between the selected individuals and the entire population

  • If negative down; If positive up

• h² = heritability (0-1)

  • 0 = no heritability

  • 1 = perfect heritability

  • If one parent is calculated multiply by 2

  • Slope of midparent/mid offspring regression

• R = Evolutionary response

  • Xoff - Xbs

Evolutionary Pattern

Phylogenetics, Speciation, Correlated Evolution

Speciation

Reproductive isolation in alloparty (other place)

• eventually those mutations (and process of selection) lead to very different population (=species)

Divergent Evolution

• Common ancestor

• 2 species look phenotypically similar because they are genetically similar “descent with modification”

• Homology

Convergent Evolution

• From different ancestors but both evolve similarly

• 2 species look phenotypically similar despite not being genetically similar. This is due to the power of having independently experienced similar agents of selection

Phylogenetic tress

Hypotheses that describe evolutionary relationships among groups

• nodes = common ancestral species

  • only 2 branches diverge from the same node

Evolutionary History

Informs current adaptive value

• Ex. Two traits of interest

  • male sword

  • female preference for swords

    • prefer to mate with longer sworded males

Evolution proceeds parsimoniously

If 2 closely related species share a trait, it is likely due to shared ancestry (homology/synapomorphy) rather than independent convergent evolution (homoplasy)

Speciation and Adaptive Radiation in Darwin’s Finches

• Beak shape evolves via reproductive isolation, differential mutation accumulation, followed by natural selection

• Sonograms of finch species song: if they look different they sound different

  • different finch species sound different

Syngamy

Fusion of gametes to form a zygote

Karygamy

Fusion of 2 gametic haploid nuclei to form diploid

Isogamous Sex

Species in which all gametes are the same size (unicellular algae and protozoa)

Sex Cost and Benefits

• Costs

  • Time

  • Two-fold Cost

  • Genome Dilution

    • only half alleles

  • STD’s

• Benefits

  • Genetic Diversity

    • beneficial mutations come together in same individual

    • Deleterious mutations purge

  • Fast evolution

Why Sex?

• Sex is a losing tactic in the short term

• Sex is a winning strategy in the long term

• Evolutionary is “patient”: large patterns are often the products of strategies, not tactics

• Almost all multicellular life is sexual

2 Sexes = 2 Strategy

• Female Strategy

  • Large investment in a small number of reproductive events

• Male Strategy

  • Small investment in a given reproductive event in a bid to have a greater number of such events

Bateman’s Principle

The choosier sex does not benefit as much (reproductive rate) from a greater number of mates

Anisogamy

Only the beginning of differential investment by the two sexes and is almost always high for females

3 Subtypes of Selection

• Viability Selection

• Fecundity Selection

• Sexual Selection

Proximate

How are behavioral traits manifested

• Mechanism

  • genetics

  • neurobiology

  • hormones

• Acquisition

  • experience-dependency

Ultimate

Why behavioral traits evolve

• Function

  • current adaptive value

• History

  • evolutionary origins

Animal Behavior

Output of the Nervous System

Nervous System Function

Processes the animal’s external and internal environments in order to respond in an appropriate manner

Nervous System Structure

• 2 Categories of neurotransmitters

  • Excitatory (depolarizing) can elicit AP in post-synaptic cell

  • Inhibitory (hyperpolarizing) inhibits AP in post-synaptic cell

Sensory Systems

Stimuli have to encoded: converted in brain to patterns of action potential

Rate Codes

Rate of AP

• encodes intensity of the stimulus

Place Codes

Which receptors

which central circuits are activated

• encodes “quality” of stimulus

Core Principle

Sensory systems do not evolve to convey/ accurate/complete information about the world, but rather useful (fitness relevants) information