Changes Over Time

SOL: BIO 8 a-e

• Standard BIO 8 a-e The student will investigate and understand how populations change through time. Key concepts include:

• a) evidence found in fossil records;• b) how genetic variation, reproductive

strategies, and environmental pressures impact the survival of populations;

• c) how natural selection leads to adaptations;

• d) emergence of new species; and• e) scientific explanations for

biological evolution.

Charles Darwin The Father of Evolution

History• Darwin’s World (1809 - 1875)• Height of the British colonial

period.• Beginning of the Industrial

Revolution.• New Ideas:

– Taxonomy of Carolus Linnaeus– Lyell’s “Principles of Geology”

Carolus Linnaeus

(1707 – 1778)Believed in the “Fixity of Species”

Binomial System of Nomenclature

Charles Lyell

• Father of Geology

Charles Lyell’s view of the process of formation of sedimentary rock

• Suggests that sedimentary rock is very old – therefore the species that are represented in this rock must also be old.

• Most fossils are found in sedimentary rock.

• Older fossils will be found below younger fossils.

Charles DarwinAt the age of 22, he joined a 5 year expedition aboard the HMS Beagle to map the coast of South America

The voyage of the Beagle

1. Members of a population have heritable variations.(Inheritance of traits)

Charles Darwin’s Theory of Evolution:

2. In a population, more individuals are produced than the environment can support. They compete for food and shelter. (overpopulation- struggle for survival).

3. Some individuals have adaptive characteristics that enable them to survive and reproduce better than other individuals (survival of the fittest).

4. An increasing number of individuals in succeeding generations have these adaptive characteristics (natural selection)

Darwin described his theory in the form of a long essay which he called

“On the Origin of Species”.

Concerned about the public’s response to his ideas(remember what happened to Galileo)

Arranged to publish his work …AFTER HIS DEATH !!

Publication of “On The Origin of Species” in 1859

Charles Darwin

At age 50 (1859)

At age 65 (1874)

Charles Darwin

Before publication After publication

• Through his observations made in the Galapagos Islands, Charles Darwin formulated a theory of how species change over time, called natural selection.

• Natural selection is governed by the principles of genetics.

• The change in the frequency of a gene in a given population leads to a change in a population and may result in the emergence of a new species.

• Natural selection operates on populations over many generations.

Evolution

• A change in successive generations of organisms, due to random mutation and changes in the organisms’ surroundings

• Evolution takes place through a set of processes that include: – mutation,– adaptation,– natural selection, – extinction.

Mutation• Genetic mutations and variety

produced by sexual reproduction allow for diversity within a given population.

• Many factors can cause a change in a gene over time.

Mutation• Mutations are

important in how populations change over time because they result in genetic changes to the gene pool.

• Mutations are inheritable changes because a mutation is a change in the DNA code

Mutation- a change in the DNAA mutation may

result in a:

1. favorable change or adaptation in genetic information that improves a species’ ability to exist in its environment

2. an unfavorable change that does not improve a species’ ability to exist in its environment.

Mutation- a change in the DNA

3. in a change in the genetic information that neither harms nor helps the species.

Mutation- a change in the DNA

Adaptation• Adaptations are structures,

functions, or behaviors that enable a species to survive.

Adaptation• Depending on the rate

of adaptation, the rate of reproduction, and the environmental factors present, structural adaptations may take millions of years to develop.

Natural Selection• the survival and reproduction of

the individuals in a population that exhibit the traits that best enable them to survive in their environment.

• The Survival of the Fittest

Natural Selection• Populations produce more offspring

than the environment can support.

Natural Selection• The unequal

ability of individuals to survive and reproduce leads to the gradual change in a population, generation after generation over many generations.

Natural Selection

• Organisms with certain genetic variations will be favored to survive and pass their variations on to the next generation.

• These five canine species evolved from a common ancestor through natural selection

African wilddog

CoyoteFox WolfJackal

Thousands tomillions of years

of natural selection

Ancestral canine

When humans choose organisms with specific characteristics as breeding

stock, they are performing the role of the environment

• This is called “artificial selection”

Example of artificial selection in plants: five vegetables derived from wild mustard

Artificial Selection in Animals: Dog Breeding

German shepherd

Yorkshire terrier English springerspaniel

Mini-dachshund Golden retriever

Hundreds tothousands of years

of breeding(artificial selection)

Ancestral dog

The evolution of insecticide resistance is an example of natural selection in

action

Chromosome with geneconferring resistanceto insecticide

Additionalapplications of thesame insecticide willbe less effective, andthe frequency ofresistant insects inthe populationwill grow

Survivor

Insecticideapplication

Extinction• no longer in existence; "the

extinction of a species"

• If a species does not include traits that enable it to survive in its environment or to survive changes in the environment, then the species may become extinct.

Individuals die, a species becomes extinct.

• Individuals of a population exhibit a range of variations in a trait as a result of the variations in their genetic codes.

• The evidence for evolution is drawn from a variety of sources of data, including:– the fossil record, – radiometric dating,– genetic information, – the distribution of organisms, – anatomical and developmental

similarities across species.

Fossil Record• Although there is not a complete

record of ancient life for the past 3.5 billion years, a great deal of modern knowledge about the history of life comes from the fossil record.

• The study of fossils provides strong evidence for evolution.

Hominid skulls

Petrified Trees

Ammonite casts Fossilized organic matter in a leaf

Scorpion in amber

“Ice Man”

Distribution of species

• Most marsupials live in Australia

• This supports the theory of continental drift.

Distribution of species

Geographic isolation can lead to speciation

Species• Organisms that

can breed and produce FERTILE offspring.

Adaptive Radiation• where species all

deriving from a common ancestor have over time successfully adapted to their environment via natural selection

Homologous Structures •  Body parts in different organisms

that have similar bones and similar arrangements of muscles, blood vessels, and nerves and undergo similar embryological development, but do not necessarily serve the same function; e.g., the flipper of a whale and the forelimb of a horse.

Homologous StructuresHuman Cat Whale Bat

Vestigial Structures

• Features that apparently serve no function in an organism and are allegedly holdovers from an evolutionary past. Such features, though no longer useful, are presumed to have been useful in ancestral species.

EX.: Wings in flightless birds

EX.: appendix in humans, whale pelvis, tiny snake pelvic and limb bones, and the eyes in cave-dwelling salamanders and fish that are completely blind.

Developmental Similarities

• Many species have very similar embryonic development.

• The embryo of a chicken, a pig, and a fish are almost identical at certain points in their development.

• Stephen Jay Gould’s idea of punctuated equilibrium proposes that organisms may undergo rapid (in geologic time) bursts of speciation followed by long periods of time unchanged.

• This view is in contrast to the traditional evolutionary view of gradual and continuous change