Study Guide Unit 1: Natural Selection and the Theory of Evolution

Natural Selection

A primary driver of evolution where organisms with advantageous traits are more likely to survive and reproduce.

Natural selection can only act on variation with a genetic component.

Variation

Genetic differences within a population that contribute to natural selection.

Heritability

The ability of traits to be inherited from one generation to the next.

Differential Reproductive Success

The concept that organisms with favorable traits survive longer and reproduce more.

Adaptation

Traits that enhance survival become more common in a population over time.

Directional Selection

A type of natural selection that favors one extreme phenotype, shifting the population curve.

Stabilizing Selection

A type of natural selection that favors the average phenotype, reducing variation.

Disruptive Selection

A type of natural selection that favors both extremes of a phenotype, increasing diversity.

Example of Directional Selection

Peppered Moths: An example of natural selection where darker moths became more common due to camouflage after pollution.

Evolution

The process by which genetic changes accumulate over generations. Genetic Variation must be present for Evolution to occur

Genetic Variation

Differences in DNA or genes among individuals in a population that contribute to evolution.

Mutations

Random changes in DNA that can introduce new traits into a population.

Sexual Selection

Non random mating and can result in sexual dimorphism (difference in male and female appearance)

Gene Flow

The movement of alleles between populations through migration.

Genetic Drift

Random changes in allele frequencies, particularly significant in small populations. Think Bottleneck and Founder Effects

Bottleneck Effect

A drastic reduction in population size that decreases genetic diversity.

Founder Effect

Limited genetic variation in a new population formed by a small group colonizing a new area.

Hardy-Weinberg Equilibrium

A model describing populations that are not evolving under certain conditions. When one of its five conditions are not met, the population is evolving

Hardy-Weinberg Conditions

No Mutations, Random Mating, No Natural Selection, Large Population Size, No Gene Flow

Hardy-Weinberg Equations

p+q=1 (allele frequencies)

p²+2pq+q²=1 (genotype frequencies)

Speciation

The formation of new species from existing populations due to reproductive isolation.

Allopatric Speciation

Speciation that occurs due to geographic isolation.

Sympatric Speciation

Speciation that occurs within the same geographic area due to various isolating mechanisms.

Prezygotic Barriers

Mechanisms that prevent fertilization from occurring.

Temporal Isolation

A prezygotic barrier where species breed at different times.

Behavioral Isolation

A prezygotic barrier where different mating rituals prevent interbreeding.

Mechanical Isolation

A prezygotic barrier due to incompatible reproductive organs.

Gametic Isolation

A prezygotic barrier where sperm cannot fertilize eggs.

Postzygotic Barriers

Mechanisms that occur after fertilization, affecting hybrid viability or fertility.

Hybrid Inviability

A postzygotic barrier where hybrid offspring do not develop properly.

Hybrid Sterility

A postzygotic barrier where hybrids are sterile, such as mules.

Hybrid Breakdown

A postzygotic barrier where hybrids are fertile but their offspring are inviable or sterile.

Galápagos Finches

An example of speciation where different beak shapes evolved due to isolation.

Divergent Evolution

Evolution where species with a common ancestor develop distinct traits.

Convergent Evolution

Evolution where unrelated species develop similar traits due to similar environmental pressures.

Parallel Evolution

Related species evolving in similar ways over time.

Coevolution

The influence of two or more species on each other's evolution.

Adaptive Radiation

The evolution of many species from a single ancestor, each adapted to different environments.

Fossil Record evidence for evolution

Evidence of evolution showing transitional forms between ancient and modern species.

Homologous Structures

Traits inherited from a common ancestor. Divergent evolution

Analogous Structures

Traits that serve similar functions but evolved independently. Convergent evolution.

Vestigial Structures

Reduced or non-functional structures that had functions in ancestors.

Molecular Biology

The study of genetic relationships through DNA comparisons.

Biogeography

The geographic distribution of species that supports evolutionary theory.

Embryonic Homology

Comparative embryology reveals anatomical homologies not visible in adult organisms.

Chemical Evolution

The hypothesis explaining how life arose from non-living matter through early Earth conditions.

Miller-Urey Experiment

An experiment simulating early Earth conditions that produced organic molecules.

Abiotic Synthesis of Organic Compounds

Bombardment of Earth by rocks and ice likely vaporized water and prevented seas from forming. Earth’s early atmosphere likely contained water vapor and chemicals released by volcanic eruptions. Likely formed near volcanoes or deep sea vents

Formation of Polymers/Macromolecules

RNA monomers were spontaneously produced from simple molecules. Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock

Protobionts

Aggregates of organic molecules that exhibit some properties of life.

What are the mechanisms of Natural Selection

Variation, Heritability, Differential Reproductive Success (Non-random Mating), and Adaption

Sources of Genetic Variation

Mutations, Non-Random Mating and Sexual Reproduction, Gene Flow, Genetic Drift, Natural Selection. Natural Selection, Gene Flow, and Genetic Drift are the forces that result in the most allele variation.

Modern Synthesis of Evolution

Essentially combines the Mendelian genetics with Darwinian evolution that resulted in a unified theory of evolution.

Emphasizes the

(1) Importance of populations

(2) Mechanism of natural selection

(3) Gradualism

What is the standard definition of a population and a loci

A population is a localized group of individuals capable of interbreeding and producing fertile offspring

A locus (or loci, plural) is the actual location of the gene on a region of a chromosome and is fixed when all individuals in a population are homozygous for the same allele

Genetic Drift vs Gene Flow

Genetic drift is the evolutionary mechanism where allele frequencies of a population change over generations due to change, occurs in all populations that are a finite size but has the strongest effects in small populations

Gene flow, any movement of individuals, and/or the genetic material they carry, from one population to another

Microevolution vs Macroevolution

Micro - change in allele frequencies in a population over generations (caused by NS, genetic drift, and gene flow)

Homoplasy

A type of convergent evolution where the traits that appear similar between species are due to similar environmental pressures (not common ancestry) eg bats and birds’ wings

What do cladograms not show

Limitations of cladograms include the inability to distinguish evolutionary time and relatedness between distinct species

What are the nested patterns in phylogenetic (evolutionary) trees

Homologies

How are phylogenetic trees different from cladograms

• Phylogenetic trees show the patterns of descent, not phenotypic similarity

• Cladograms show relationships between species based on shared traits but do not provide a sense of time or amount of evolutionary change.

What are branches in a phylogenetic tree and what can they represent

Branches represent evolutionary lineages

The length of the branches can represent time or amount of evolutionary change in some trees

Differences between Monophyletic, Paraphyletic, and Polyphyletic Groups

Monophyletic, Paraphyletic, and Polyphyletic Groups:

• Monophyletic Group (Clade): Includes a common ancestor and all its descendants (e.g., all mammals).

• Paraphyletic Group: Includes a common ancestor and some, but not all, of its descendants.

• Polyphyletic Group: Includes species with different ancestors, grouping them based on similar traits that evolved independently (e.g., winged organisms like bats, birds, and insects).

Ancestral Trait vs Derived Trait

Ancestral = present in a common ancestor of a group of organisms

Derived=evolved in one or more members of a group but not present in the common ancestor

What are nodes, roots, and outgroups of a cladogram

Every branching point in a cladogram are nodes and represent a common ancestor that gave rise to two or more species

Roots are the base of the cladogram

Outgroups are a species or group that is closely related to, but not part of, the group of species being studied. It helps determine the evolutionary direction of traits

What can fossil records document for evolution

Show how a species evolves into two distinct groups (different groups)

What is the common isotope for fossil dating

carbon-14

what is biogeography’s role in evidence of evolution

Pangaea and continental drift allows us to predict when and where different groups evolved

Theory of plate tectonics

Earth’s crust is composed of plates floating on Earth’s mantle

Intrasexual selection vs intersexual selection

Intrasexual selection is competition among individuals of one sex for mates

Intersexual selection - individuals of one sex are choosy in selecting their mates

Auto- vs Allo- polyploidy

Auto - an individual with more than 2 sets of chromosomes derived from one species

Allo - a species with multiple sets of chromosomes derived from different species

Many plants are polyploids

What are the 4 general prezygotic barriers

Temporal Isolation, Behavior Isolation, Mechanical Isolation, and Gametic Isolation.

Temporal - different times of mating

Behavioral- Courtship rituals and other behaviors

Mechanical - morphological differences

Gametic - sperm of one species cannot fertilize the eggs of another species

Binomial Nomenclature

Homo sapiens

First part of name is genus, second part is the epithet which is unique for each species within the genus

Linnean System of Classification

taxonomic groups (taxons) are broad then narrow

Domain, kingdom, phylum, class order, family, genus, and species

Differences in each of the domains

Bacteria - peptidoglycan in the cell walls, one type of RNA polymerase, rarely have introns in genes

Archaea - no peptidoglycan, several kinds of RNA polymerase, occasional have introns in genes

Eukarya - membrane bound organelles, several types of RNA polymerase, have introns in many genes

Are eukarya and archaea more related or archaea and bacteria

eukarya and archae are more related

Steps in origin of life

1. Abiotic Synthesis of Organic Molecules

2. Formation of Polymers (macromolecules)

3. Formation of Protobionts/Protocells

   1. Endosymbiosis

4. Development of Self-Replicating Molecules

   1. RNA world hypothesis

Cyanobacteria

autotrophic bacteria that respirate. important to the food chain as producers

Parsimony

the basic scientific principle to choose the simplest scientific explanation that fits the evidence

The more complex two similar structures are the more likely it is that they are _______

homologous

Dynamic Hypotheses

Cladistics and Phylogenetic trees can be dynamic and adjusted according to new or conflicting information

Horizontal Gene transfer

The movement of genes from one genome to another. Occurs by exchange of transposable elements (DNA sequences) and plasmids (extrachromosomal DNA molecule for bacteria) , viral infection, and fusion or organisms.

Self-Replicating RNA origin

First genetic material, ribozymes, found to catalyze the different reactions. Could’ve formed the template for DNA

RNA World Hypothesis origin

Natural selection produced self-replicating RNA molecules. The more stable/fit ones were left with the most descendants. Formed an RNA world (all stuff was RNA)

Protocells + origin

vesicles with RNA capable of replication. the abiotic precursor of a living cell. May have been fluid filled with a membrane like structure.

May have formed from lipids and other organic molecules spontaneously forming vesicles with a lipid bilayer in water (adding clay increases rate of vesicle formation). Exhibited simple reproduction and metabolism and basic chemical homeostasis

stromatolites

oldest known fossils. rocks formed by the accumulation of sedimentary layers on bacterial mats (3.5 bya)

Oxygen Revolution

O2 produced by photosynthesis reacted with iron and precipitated banded iron formations. O2 accumulated in the atmosphere rusting the iron rich rocks.

Caused the extinction of many prokaryotic groups. The ones that survived adapted to use cellular respiration to get energy

Likely caused by cyanobacteria, later rise due to evolution of eukaryotic cells containing chloroplasts

First Eukaryotes

Have nuclear envelope, mitochondria, endplasmic reticulum and cytoskeleton

Evidence for endosymbiosis

inner membranes are similar to plasma membranes of prokaryotes.

organelles transcribe and translate their own DNA

similar ribosomes to prokaryotes rather than eukaryotes

All eukaryotes have _________ (4 things)

cytoskeleton, membrane bound organelles, linear chromosomes, and endomembrane systems

First multicellular eukaryotes

1.5 bya, oldest known fossil is a small algae that lived ~1.2 bya

snowball earth hypothesis

suggests that periods of extreme glaciation confined life to the equator regions and deep sea vents from 750 to 580mya because the ediacaran biota were larger more diverse soft bodied organisms that lived after snowball earth

Cambrian explosion

the sudden appearance of fossils resembling modern animal phyla 535-525 mya.

the sponge, cnidarians, and molluscs appear earlier.

first evidence of predator prey interactions

Colonization of Land

Fungi, plants, and animals began to colonize land ~500mya. Vascular tissue in plants appeared by ~420 mya.

Mutually beneficial relationships between plants and fungi. Arthropods and tetrapods are the most widespread and diverse land animal

Tetrapods

evolved from lobe-fined fishes ~365 mya with limbs and digits

What had a complex nervous system and elaborate skeleton

Vertebrates and Land Vertebrates

Earliest vertebrates

soft bodied jawless vertebrates called conodonts. the surviving jawless vertebrates are the lampreys and hagfish

the most primitive tetrapods are ___

amphibians

What are amniotes

Amniotes are a group of vertebrates that lay eggs on land or retain them within the mother. This group includes reptiles, birds, and mammals.

They are characterized by the presence of an amniotic egg, which has protective membranes that allow for the development of the embryo in a terrestrial environment.

Where did birds originate from

saurischian dinosaurs. they are considered reptiles

what is MRSA

Methicillin-resistant Staphylococcus aureus

S. aureus became resistant to penicillin in 1945 and to methicillin in 1961; bacteria continue to evolve.

Developed antibiotic resistance through the production of a protein called PBP2a in their cell walls, which is able to avoid the inhibitory effects of the antibiotics