The Origin of Life

Stage 1: Abiotic Synthesis of Organic Monomers Amino Acids

Chains of nucleotides Chains of DNA bases Chains of RNA bases

Building blocks of protein Sugars Lipids ATP

The Origin of Life

Stage 2: Abiotic Synthesis of Polymers Monomers, such as amino acids,

spontaneously fused together to form proteins.

The Origin of Life

Stage 3: Origin of Self-Replicating Molecules

inheritance

Ribozyme: catalytic RNA used to fuel RNA replication

The Origin of Life

Stage 4: Formation of Pre-cells Molecular packages

with some properties of life.

The gap between pre-cells and true cells is enormous! Natural Selection

The origin of eukaryotic cells

Endosymbiotic Theory

Membrane bound nuclear material

Organelles More complex than

prokaryotic cells Ancestors to fungi, plants

and animals

Concept Map

Evolution of LifeSection 17-2

Early Earth was hot; atmosphere contained poisonous gases.

Earth cooled and oceans condensed.

Simple organic molecules may have formed in the oceans..

Small sequences of RNA may have formed and replicated.

First prokaryotes may have formed when RNA or DNA was enclosed in microspheres.

Later prokaryotes were photosynthetic and produced oxygen.

An oxygenated atmosphere capped by the ozone layer protected Earth.

First eukaryotes may have been communities of prokaryotes.

Multicellular eukaryotes evolved.

Sexual reproduction increased genetic variability, hastening evolution.

HISTORY OF EVOLUTIONARY

THEORY

Evolution = “Descent with Modification”

1. ------------due to being spread over different habitats and therefore adapting and modifying themselves to fit the habitat.

2. Natural Selection

• A population of organisms can change over generations if certain inheritable traits leave more offspring than others and those others get the chance to reproduce and continue the lineage.

• Evolutionary Adaptation

THE ROAD TO EVOLUTIONARY THEORYEvolution Before Darwin

Greek Philosophers

• Plato’s Idealism

• Aristotle’s scala naturae (scale of nature)

special creation of each species organisms were created in their

current form the earth was only a few thousand

years old

THE ROAD TO EVOLUTIONARY THEORY

Evolution Before DarwinTHOMAS MALTHUS

economist & clergyman

published An Essay on the

Principle of Population

Populations had an inherent tendency to increase geometrically, while the resources needed to support this growth increase slowly or not at all.

Because of the continued growth of a species would outstrip needed resources, growth would be limited.

THE ROAD TO EVOLUTIONARY THEORY

Evolution Before DarwinJEAN-BAPTISTE de LAMARCK

French biologist

proposed that modern species descended from other species

Lamarckism based on two theories:

1. Inheritance of Acquired Characteristics- traits acquired by an individual during its life are passed to its offspring

2. Use and Disuse- organs of the body that were used extensively to cope with the environment became larger and stronger, while organs that were not used deteriorated

Example:

The Evolution of the Giraffe

Giraffes obtained their long necks from previous giraffes who stretched to eat the leaves of high tree branches.

Stretching increased the length of their necks, and this acquired characteristic was passed to the next generation.

THE ROAD TO EVOLUTIONARY THEORYEvolution Before Darwin

THE ROAD TO EVOLUTIONARY THEORYEvolution Before Darwin

Lamarckism

first to present a unified theory that attempted to explain the changes in organisms from one generation to the next

Although, mechanisms proposed for change was wrong, since acquired characteristics are not heritable!!!

origin of species from preexisting species ability of organisms to adapt

THE ROAD TO EVOLUTIONARY THEORY

Darwin’s Time (1800s)GEORGES CUVIER

French anatomist and naturalist and writer

palaeontologist

strongly opposed the concept of evolution

history of living organisms recorded in layers of rock containing a succession of fossil species in chronological order

fossils were organisms that had died in a series of catastrophes, after which extinct plants and animals were replaced by the immigration of distant species to the devastated region Catastrophism

THE ROAD TO EVOLUTIONARY THEORY

Darwin’s Time (1800s)

CHARLES DARWIN

voyage on the H.M.S. Beagle (1836)

published (1859)The Origin of Species

first person who proposed a mechanistic approach to evolutionary thought

the father of synthetic evolution

The Voyage of the Beagle

On the Galapagos Islands...

Galapagos tortoise

Darwin’s finches

Most organisms on the islands were endemic.

His Conclusions:

The birds were very similar (common ancestry).

They all adapted to different Niches. Niche = Your job in nature.

What you eat Where you live (on ground, in a tree)

Reproductive Isolation resulted in speciation.

Evolutionary Adaptation

Evidence of Evolution:Fossil Record

Fossils chronologically ordered in rock layers

Evidence of Evolution:Biogeography

Geographic distribution of species: Australian marsupials

Evidence of Evolution:Comparative Anatomy and Embryology

HOMOLOGY

Evidence of Evolution:Molecular Biology

Notice that a Chimp is more genetically related to a human than to an Old World Monkey!

species not specially created in their present forms, but had evolved from ancestral species

proposed a mechanism for evolution:

Natural Selection

A population of organisms can change over time as a result of individuals with certain heritable characteristics leaving more offspring than other individuals.

Radioactive Dating

Darwinism in Historical Context

THE ROAD TO EVOLUTIONARY THEORY

Darwin’s Time (1800s)GREGOR MENDEL

Austrian biologist

discovered the basic principles of heredity

father of Classical Genetics

Individual characteristics determined by inherited factors transmitted from parent to offspring.

THE ROAD TO EVOLUTIONARY THEORY Neo-Darwinian/Contemporary Times

rediscovered Mendel’s laws of heredity

the start of rediscovering evolution in terms of Mendel’s ideas

HUGO DE VRIES

CARL CORRENS

ERICH VON TSCHERMAK

THE ROAD TO EVOLUTIONARY THEORY

Neo-Darwinian/Contemporary Times

JAMES WATSONFRANCIS CRICK

elucidated the structure of DNA (genetic material)

DNA contains coded information which acts as a blueprint for the transfer of hereditary information from generation to generation

mutation as the raw material for evolution

Darwinism Meets Genetics A population is the smallest unit of evolution.

Natural selection acts on individuals. However the evolutionary impact of natural selection is

only apparent in tracking how a population changes over time.

Population Genetics emphasizes the extensive genetic variation within populations and tracks the genetic make-up of populations over time. Not all variation in a population is inheritable. Only the genetic component of variation is relevant to natural

selection. Many variable traits in a population result from the combined

effect of several genes.

Hardy-Weinberg Principle

Genetic equilibrium- allele frequenciesremain constant. Populations should be in a state of

equilibrium assuming: 1. Large Population 2. Random Mating 3. No Migration 4. No Mutation 5. No natural selection occurs.

Variables Needed to maintain Equilibrium:

Perfectly adapted organsim. Sharks Alligator Horseshoe Crab

Stable envrionment. Water (Oceans)

Punctuated Equilibrium

Speciation occurs relatively quickly with long periods of equilibrium in between. Speciation = The formation of a new species

due to evolution.

Genetic Drift

Evolution can occur without natural selection.

Genetic Drift is a change in the gene pool due to a random event. Example- Mount Saint Helens Eruption.

If the event is catastrophic and all the organisms are killed off = Mass extinction.

Speciation

= The formation of a new species due to evolution.

Reproductive Isolation- Can result in speciation. It is the separation of members of a species due to some barrier. Islands Mountains Roads Oil Pipes

• Speciation occurs only with the evolution of reproductive barriers between the isolated population and its parent population.

• If speciation occurs during geographic separation, the new species will not breed with its ancestral population, even if the two populations should come back into contact.

Mechanisms of Speciation

Allopatric Speciation A population forms a

new species while geographically isolated from its parent population.

Sympatric Speciation A small population

becomes a new species in the midst of a parent population

Sympatric Speciation

Does not widely occur among animals but may account for over 25% of all plant species.

Notice how the hybrid bread wheat has a set of chromosomes from each of its ancestors: T. monococcum (AA), Triticum (BB), T. turgidum (AA BB), T. tauschii (DD)

What can you notice about T. aestivum that might make it a good hybrid and the most important wheat species today?

Evolutionary Patterns

Convergent Evolution- Organisms of different ancestry adapting to a similar environment. Produces homologous Structures. Example: bats and Butterflies wings.

Dolphin Penguin Shark

Divergent Evolution- Organisms of common ancestry adapting to diverse environments. Produces analogous Structures. Example: Human Arm and Bird wing.

Microevolution1. Genetic Drift Def: A change in the gene pool of a small population due

to chance.

The best measure of Darwinian fitness is the number of fertile

offspring an individual leaves.

Microevolution Cont.2. Gene Flow

Def: The genetic exchange with another population.

3. Mutations A change in an organism’s DNA sequence. Ultimate source of genetic variability.

4. Natural Selection Directional Selection (selecting in favor of an extreme

phenotype) Disruptive (Diversifying) Selection (leads to a balance between

two or more contrasting phenotypic forms) Stabilizing Selection (maintains variation in a narrow range)

• Resistant Genes

• Immediate Benefits

• Long term Disaster

• Evolution direct connection to daily lives

Macroevolution

Def: Major biological changes evident in fossil record.

CONTRAST: MICROEVOLUTION

Speciation Nonbranching evolution

(transform a population enough for it to be designated a new species.)

Branching evolution (splits a lineage into two or more species)

The Origins of Species Ernst Mayr

Studied the diversity of birds in New Guinea (1927) Biological species concept

Species = “groups of interbreeding natural populations that are reproductively isolated from other such groups.”

Reproductive isolation blocks exchange of genes between species and keeps their gene pools separate.

• Reproductive barriers between species• Zygote: fertilized egg• Pre-zygotic (factors that impede

mating between species or hinder fertilization of eggs if mating is attempted)

• Post-zygotic (mechanisms that operate should interspecies mating actually occur and form hybrid zygotes)

Courtship

Sterile

Isolating Mechanisms

Tempo of Evolution

Slow adaptations

Spurts of relatively rapid change

Section 17-4

Flowchart

that are

can undergo can undergo can undergo can undergo can undergo

in underunderform inin

Species

Unrelated Related

Inter-relationshiops Similar environments

Intense environmental

pressure

Small populations

Different environments

Coevolution Convergent evolution

ExtinctionPunctuated equilibrium

Adaptive radiation

Classifying the Diversity of Life

Systematics Reconstructing evolutionary history Radioactive dating = tool The study of biological diversity: past and

present Taxonomy

Identification, naming and classification of species

Pioneer: Carolus Linnaeus (1707-1778) Binomial Nomenclature Homo sapien

Hierarchical Classification

Which step is more specific?

Class or Genus?

How is Domain Eukarya different from Bacteria and Archaea?

Phylogeny• Evolutionary

history of a species.

• Tree is based on homologous structures, NOT analogous.

• Two species will have more common nucleotide sequences based on how recently they branched from their common ancestor.

The Cladistic Revolution

The Computer Age

6 Kingdoms vs. 3 Domains

?Eubacteria

Archaea-bacteria