evolution: change over time

EVOLUTION:

CHANGE OVER TIME

In Biology…evolution refers to:

• Changes in SPECIES over time

• A species is a group of similar organisms that can breed and produce fertile offspring.

CHARLES DARWIN• Proposed the theory of

evolution• He made observations on

his voyage around the world…collecting evidence to develop his theory.

• On the Origin of Species (Book—1859)

IMPORTANT OBSERVATIONS

1. Noticed a great diversity among a number of species.

2. Plants and animals were suited to the environment in which they lived.

3. Different species lived in similar ecosystems.

FOSSIL RECORD

• A fossil is the preserved remains of ancient organisms.–Some looked like

modern animals–Some looked different

than any modern organisms

The Galapagos Islands• Very close to one

another…but their climates differed greatly-–Low elevation: very dry,

hot, sparsely vegetated–Higher elevation: a lot of

rainfall, more diverse plant life

The Galapagos Islands

Galapagos Tortoises

Saddleback Domed

FITNESS

• Organisms compete to survive and reproduce

• Organisms best suited to their environments are most likely to succeed

FITNESS is attributed to:

• Adaptations–Any inherited trait that

increases an organism’s chance of survival

NATURAL SELECTION

• SURVIVAL OF THE FITTEST—–Those that are able to

survive will be able to reproduce and pass on their adaptations to the next generation

NATURAL SELECTION (4 Principles)

1. VARIATION EXISTS WITHIN POPULATIONS

NATURAL SELECTION (4 Principles)

2. ORGANISMS COMPETE FOR LIMITED NATURAL RESOURCES

NATURAL SELECTION (4 Principles)

3. ORGANISMS PRODUCE MORE OFFSPRING THAN CAN SURVIVE

NATURAL SELECTION (4 Principles)

4. INDIVIDUALS WITH VARIATIONS SUITABLE FOR THEIR HABITAT SURVIVE AND REPRODUCE

FINCHES

TWO WAYS EVOLUTION MAY OCCUR

• GRADUALISM– Occurs over a long period of time

• PUNCTUATED EQUILIBRIUM– Occurs in spurts– Caused by:

• Random change in DNA• Sudden environmental changes

CONTINUITY OF LIFE FORMS

OVER TIME

TWO FORMS OF EVOLUTION• MACROEVOLUTION

–changes that occur on the tree of life

• MICROEVOLUTION–Changes that occur within a

population– (group of individuals of the

same species living in the same area)

• Genetic variation is caused by changes in genetic frequency—there are 5 forces of genetic change:1. Natural Selection2. Mutations3. Gene flow4. Genetic drift5. Nonrandom mating

MUTATIONS• Change in DNA sequence

–Deletion–Inversion–Translocation–Duplication

…however…

MUTATIONS• To affect evolution,

mutations must be passed on from one generation to the next…

• Only mutations in gametes can be passed on…

• …to affect evolution!

GENE FLOW• Genes from one population

are introduced into the gene pool of another

• GENE POOL: combined genetic info of all members

• Basically affected by migration

GENETIC DRIFT• Changing the allele

frequency• Some individuals may have

more offspring than others

BOTTLENECK EFFECT• A form of genetic drift• Sudden and severe

decrease in a population size that results from natural disaster, predation, or habitat reduction.

Bottleneck Effect

FOUNDER’S EFFECT• A form of genetic drift• occurs when a new isolated

population is founded by a small number of individuals possessing limited genetic variation (relative to the larger population from which they have migrated)

Founder’s Effect

http://upload.wikimedia.org/wikipedia/commons/2/24/Founder_effect-anim.gif

NONRANDOM MATING• Not all individuals have the

opportunity to contribute their genes to the next generation (decreasing their allele frequency)

• Courtship rituals, pecking orders, breeding territories

MECHANISMS OF CHANGE

NATURAL SELECTION

MUTATIONS

GENETIC DRIFT

GENE FLOW (MIGRATION)

NATURAL SELECTION

Peppered Moths

• Number of current classified species =

• 2.1 million

• Organisms that are not capable of breeding with each other belong to a different species

• What causes new species to form?

»The evolutionary process called SPECIATION forms new species.

»New species evolve in 3 ways….

1. GEOGRAPHIC ISOLATION• A population is divided by a

barrier • Two geographically isolated

populations can no longer reach each other to breed

• Natural selection on each side causes the populations to become genetically different

1. GEOGRAPHIC ISOLATION

2. PARAPATRIC SPECIATION• Two neighboring populations

– One hot and dry– One cooler and wet

• Natural selection favors different adaptations in area– Causing genetic differences

• At the boundary—individuals breed and make hybrids…

2. PARAPATRIC SPECIATION

3. BEHAVIORAL ISOLATION

• Differences among individuals cause them to choose different mates.

• Continual, nonrandom mating causes individuals to become genetically different.

3. BEHAVIORAL ISOLATION

EXTINCTION• The death of all individuals

within a species.• No longer able to survive

changing environmental conditions

-or-• No longer able to compete

EVIDENCE OF

EVOLUTION

FIELD OF PALENTOLOGY• Fossils are “dead remains”

that prove organisms existed

• Give information about the age of organism (dating)

• PROBLEMS??–Still missing links–Haven’t found all remains

FIELD OF BIOGEOGRAPHY• Geographic distribution of

organisms• Grouped according to the

needs of habitats, resources

• Similar organisms will arise in the same geographic location

Ostrich (Africa)Rhea (South America)

Emu (Australia)

FIELD OF BIOCHEMISTRY• All living things have DNA• Organisms that show

close relationships have similar protein and DNA structures

BIOCHEMISTRY

BIOCHEMISTRY

FIELD OF ANATOMY

1. Homologous structures–Have similar construction–Example:

•Human arm•Cat leg•Whale flipper•Bat wing

ANATOMICAL HOMOLOGY

FIELD OF ANATOMY

2. Analogous structures–Serve the same purpose–BUT not designed in

same way–Example:

•Bird wing• Insect wing•Bat wing

ANALOGOUS STRUCTURES

FIELD OF ANATOMY

3. Vestigial structures–Seen in organisms of

today but not used–Example:

•Appendix •Tail bone•Whale legs•Snake legs

VESTIGIAL STRUCTURES

FIELD OF EMBRYOLOGY• (embryo development)• Very early stages of

development in animals are hard to distinguish between different animals

EMBRYOLOGICAL HOMOLOGY

IDENTIFY THE ORGANISMS

EMBRYOLOGICAL HOMOLOGY

HOW ABOUT NOW?

EMBRYOLOGICAL HOMOLOGYWOW !

EMBRYOLOGICAL HOMOLOGY

PATTERNS OF

EVOLUTION

COEVOLUTION• Change in two or more

species in close association with each other

• Change occurs to benefit each other

• EXAMPLE:– Animals and their plants– Hummingbird and trumpet flower

COEVOLUTION

DIVERGENT EVOLUTION• Two or more related

species become different

CONVERGENT EVOLUTION• Ancestors were different

and become similar

DIVERSITY

DIVERSITY• TAXONOMY

–Science of naming and then classifying living things

• CLASSIFICATION–Systematic grouping of

organisms based on common characteristics

• Kingdom• Phylum• Class• Order• Family• Genus• Species

Kids Prefer Cheese Over Fried Green Spinach

• Scientists attempt to understand the evolutionary relationships among organisms…

• PHYLOGENETICS–Studies the

relationships among organisms

• PHYLOGENETIC TREE:–Diagram that represents

the evolutionary history of a species

PHYLOGENETIC TREES ARE USED TO CLASSIFY:

• Organisms into major taxa (groups) based on evolutionary relationships

• Species in the order in which they descended from a common ancestor using physical characteristics

PHYLOGENETIC TREE

PHYLOGENETIC TREE

PHYLOGENETIC TREE

PHYLOGENETIC TREE

• Which groups are most closely related?

• Which groups are least closely related?

• Which group diverged first (longest ago) in the lineage?

Charles Darwin

• Discuss Darwin’s contributions to how living things change over time.

• Discuss evidence for how living things change over time—including homology, biogeography and fossil record.

• Discuss the five conditions preventing living things from changing over time (Hardy-Weinberg). What conclusions can you draw based on this information?

• There are several agents (mechanisms) for how living things change over time, focus your research on the following: genetic drift (including the founder’s effect and bottleneck effect) and gene flow.

• There are several agents (mechanisms) for how living things change over time, focus your research on the following: natural selection and mutations.

• What misconceptions did you have prior to your research? What are your conclusions?

Hardy-Weinberg

• What Is Hardy-Weinberg?

• How does it work?

Hardy-Weinberg Conditions

1. No Genetic Drift (Infinite Population Size)2. No Migration (No Gene Flow)3. No Mutation4. No Selection (No Differential Selection)5. Random Mating (No Differential Reproduction)

Founder’s Effect

SURVIVAL OF THE FITTEST

Everyone with blue eyes can be traced back 10,000 years to the Black Sea region. Throughout history they have been the eyes that are prized. Frank

Sinatra's were legendary, Paul Newman's melted a million hearts while Cameron Diaz's dazzle in modern Hollywood.

But how - and why - blue eyes arose has always been something of a genetic mystery. Until now.

According to a team of researchers from Copenhagen University, a single mutation which arose as recently as 6-10,000 years ago was responsible

for all the blue-eyed people alive on Earth today.

The team identified a single mutation in a gene called OCA2, which arose by chance somewhere around the northwest coasts of the Black Sea in

one single individual, about 8,000 years ago.

The gene does not "make" blue in the iris; rather, it turns off the mechanism which produces brown melanin pigment. "Originally, we all

had brown eyes," says Dr Hans Eiberg, who led the team.And most people still do. The finding that a rare mutation, probably

dispersed in the rapid wave of colonization that followed the end of the last ice age, highlights one of the great mysteries of human evolution: the

oddness of Europeans.

One theory is that Europe's cold weather and dark skies played a part. Fair skin is better at making Vitamin D from the 8 per cent of the world's

population have blue eyes weak sunlight found in northern latitudes.

Perhaps the most plausible theory is that blonde hair and blue eyes arose because of a mechanism called sex selection.

This is where males and females choose as their mates those who have one unusual physical characteristic, not necessarily associated with

"fitness" per se but simply something unusual.The gigantic (and otherwise useless) tail of the peacock is the best

example.

All blue-eyed people can be traced back to one ancestor who lived 10,000 years

ago near the Black SeaBy MICHAEL HANLON

VARIATION

THE NEW FACE OF

AMERICANovember 18, 1993

IMAGES• ANATOMICAL HOMOLOGY• EMBRYOLOGICAL HOMOLOGY• VARIATION• MECHANISMS OF CHANGE• NATURAL SELECTION• FINCHES• GIRAFFES• THE NEW FACE OF AMERICA• BLUE EYES• FROGS