BIO 112 Basu EXAM 1

Aristotle

-Fixed ideal species

-Scala Naturae (scale/ladder of nature) Humans at the top, followed by mammals, birds, etc.

Age of Reason (1700s-1800s)

Birth of science. (start of observations, thinking, and reasoning)

Linnaeus

-created the orderly binomial naming system

James Hutton

Father of gradualism (earth is always changing geographically over time)

Charles Lyell

-Father of geology

-Uniformitarisnism: same geographical processes in past as today

-EARTH IS EXTREMELY OLD

Erasmus Darwin

Natural philosopher, Development of life over eons

Lamark

-Naturalist

-Extinct species have been replaced by descendants w/ new features

-First to propose mechanism for evolution

-Lamarkism: inheritance of acquired traits (WRONG)

Charles Darwin

-Naturalist

-Collected a lot of wildlife, plants, and fossils from the Galapagos islands

-Famous for the theory of evolution

The Theory of Evolution

-Darwin wrote his essay in 1844

-Alfred Wallace came up with same idea and wrote Darwin in 1858

-Both co-published in 1858

Origin of Species (1859)

1. Descent with Modification

2. Natural Selection

Natural Selection

-unique idea by Darwin

-"descent through modification"

-Natural Selection is a mechanism for evolution

Natural Selection & evolution

1) heritable variation

2) can enhance small variations through artificial selection

3) All species produce more offspring than the environment can hold

4) Adaptations that help survivability can accumulate for max. success

5) Environment controls evolution

NOT explained in Darwin's Theory

origin of life, how variation arises, how inheritance works, why variation still exists, "sudden" changes in fossil record, Source of totally "new" characters (Most are now explained)

Evidence of Darwin's Theory

1. Fossil record

2. Homology

3. Convergence

4. Biogeography

5. Molecular Biology

Homology

-similarity in structure from common ancestor

-structure modified for different functions

analogous structures

-Body parts that share a common function, but not structure

-different species

Vestigial Structures

-Homologous

-no present adaptive function

Convergence

-analogous

-natural selection acted the same in same conditions

Biogeography

-distribution of species via geographic history

Gene Flow

Movement of alleles across a species' range

Ways to define species

Morphological species

Ecological Species

Phylogenetic species

BIOLOGICAL SPECIES

Biological species concept

Organisms that are reproductively isolated from each other are different species. biological barrier

Morphological Species Concept

Organisms that have significant morphological and anatomical differences are different species

Pre-zyotic Barriers

Prevent fertilization: Temporal isolation (ex: different mating times), Behavioral isolation (ex: different mating calls/courtship cues, Habitat isolation (ex: ecological, different habitats), Gametic isolation (ex: gametes cant fuse-different flowers have different pollen), Mechanical isolation (ex: certain dog breeds cannot breed with each other bc of size)

post zygotic barriers

act after a hybrid zygote is formed, reduced hybrid viability (may be born but fails to develop), reduced hybrid fertility (born but sterile),hybrid breakdown (1st generation is vaible but 2nd generation fails)

Gene & Reproductive isolation

A gene may influence reproductive success, snails can only mate with other snails with the same shell rotation

Problem with biological species concept*

-fossil species

-asexual species

-hybrids do happen

Speciation

Formation of new species

Allopatroc Speciation

-In which a population forms new species because its geographically isolated from the parent population (Panama land bridge, mosquitofish)

adaptive radiation

An evolutionary pattern in which many species evolve from a single ancestral species (finches), organisms diversify due to environmental changes ex: Hawaii Honeycreeper bird -> evolved to multiple other birds with different characteristics

What causes speciation?

changes (mutations), sexual selection, reproductive incompatibility

sympatric speciation

The formation of new species in populations that live in the same geographic area (cichlids and muddy water), Same geographical area, rare

Chromosomal Errors

-sympatric speciation

-aneuploidy 2n + 1 or 2n - 1 (too many or too few chromosomes, non disjunction)

-polyploidy 4n

habitat differentiation

sympatric speciation can also result from the appearance of new ecological niches

Gradual speciation

species diverge gradually over time in small steps

punctuated equilibrium

species evolve during short periods of rapid change followed by long periods of stasis

allopolyploidy

-polyploidy resulting from contribution of chromosomes from two or more species (rarely found in animals, mostly plants)

-normal gamete + polyploid gamete = polyploid gamete -> second mating -> allopolyploidy

Phenotypic relations

mostly genetic but environment can influence expression

Discrete genetic variation

Variation in a single gene locus

Continuous Variation

phenotypes produced by combined effects of 2 or more genes

How do new alleles arise?

mutations in the DNA

What is a population?

a group of individuals of the same species living in the same area at the same time

Allelic frequency

the percentage of any specific allele in the gene pool

Genetic frequency

refers to the percentage of each allele for a particular trait in a population

Microevolution

any change in a populations allelic genotypic frequency over time

Hardy-Weinberg Principle

principle that allele frequencies in a population will remain constant unless one or more factors cause the frequencies to change

Hardy-Weinberg conditions

1. No mutations

2. Random mating

3. No natural selection

4. Extremely large population size

5. No gene flow

Hardy-Weinberg equation

p2 + 2pq + q2 = 1

What if a population meets the H-W equation?

every generation over time will have the same genotypic rations

What is H-W used for?

-Used to determine population's genetic makeup

-if the actual ratios do not equal HW ratios then the population is evolving

Mechanism of microevolution

1. natural selection

2. genetic drift

3. Founder Affect

4. Bottleneck Effect

5. Gene Flow

Natural Selection

-acts non-randomly on phenotypes of individuals

-changes allelic & genotypic frequencies of populations

-always leads to adaptation of population to current environment

Aspects of natural selection

1) relative fitness

2) directional selection

3) disrupted selection

4) Stabilizing selection

Genetic Drift

-random

-occurs in small populations (like sampling errors in statistics)

Outcomes

-one allele may become fixed

-random changes in allele frequency

Founder Affect

-genetic drift resulting from the colozination of a new isolated population

-founder gene pool is different from original species

-small population —> more drift

-superior alleles may be lost

Bottleneck Effect

-genetic drift that dramatically cuts population size

-gene pool survivors are lost

Gene Flow

-alleles move in/out of population

-migration

-dispersal of gametes, seeds, larvae

Results of gene flow *

-adds diversity to population

-reduce differences between populations

Forms of Natural Selection

-Directional

-Diversifying

-Stabilizing

-Frequency-Dependent Selection

-Sexual Selection

Macroevolution

Gene flow + 3.8 billion years

Relative Fitness

Best reproductive success

Directional Selection

-shifts populations genetic variance toward the new, fit phenotype

-selects phenotypes at one end of the spectrum (mouse fur color)

Diversifying Selection

-intermediates are less fit than extremes

-maintains diversity

-increases genetic variance

Stabilizing Selection

-intermediate types more fit than extremes

-decreases genetic variance

Frequency-Dependent Selection

-the fitness of a phenotype depends on how common

Sexual Selection

=success based on traits related to obtaining mates

-leads to sexual dimorphism

Intrasexual Selection

Individuals in one sex compete

Intersexual selection

Mate choice (usually females)

sexual dimorphism

Differences between the sexes in secondary sexual characteristics.