Changes through time Survival of the Fittest. Evidence that life has changed and is now changing

Changes through time

“Survival of the Fittest”

Evidence that life has changed and is now changing

Fossil Record

Fossils are remains or traces of organisms that lived in the past.

Fossil Record

Fossils are usually found in sedimentary rock.

Organisms are buried soon after death and the hard parts become fossilized.

Fossil Record

Fossils indicate a great deal about the actual structure of the organisms and their environment.

Types of fossils

Petrified Bones

Types of fossils

Imprints

Types of fossils

Molds/Casts

Types of fossils

Fossils preserved in tar, amber, or ice

Relative Age of Fossils

Layering of fossils:Older fossils are found in the lower levels of sediment

Relative Age of Fossils

Layering of fossils: Newer fossils

deposited on top of older fossils and sediment

Sometimes flipped by earthquakes, etc.

Relative Age of Fossils

Relative Age of Fossils

Fossils in each layer usually of those organisms that lived at the time the layer was formed.

Fossils in lower layers represent species that lived earlier than those found in the upper layers.

Relative position only tells which are older and which younger.

Evolution of the Horse Over time (higher layers

of sediment) horse fossils became larger

Separate toes became a single-toed hoof

Teeth became adapted to grinding grasses

Radiometric Dating

Some elements, such as uranium, undergo radioactive decay to produce other elements.

Scientists have observed that radioactive elements (isotopes) decay at a constant rate over time

Radiometric Dating

The amount of radioactive elements remaining in a rock can help scientists determine how much time has elapsed since the rock was formed and cooled.

Common isotopes used for long-term dating (old rocks) include uranium as it decays to lead, and potassium as it decays to argon.

The carbon-14 isotope can be used for dating of more recent fossils and artifacts

Radiocarbon Dating

Carbon-14 is a radioactive isotope found in all living organisms. It decays at a known rate.

Carbon-12 does not decay. By comparing the ratio of C-12 to C-

14 scientists believe they can determine the age of a fossil

Radiocarbon Dating

A timescale

Based on radiometric data, scientists have proposed a timeline for the history of the earth.

Composed of four primary “eras” Archeozoic (oldest) [aka Precambrian

period] Paleozoic Mesozoic Cenozoic (most recent)

Contemporary Changes

Evidences we can observe within our lifetime Pesticide resistance in insects

Contemporary Changes

Evidences we can observe within our lifetime Antibiotic resistant bacteria

Indirect evidences

Scientists cite these indirect evidences as evidence of common ancestry Homologous structures Embryonic development patterns Biochemical evidence Vestigial organs

They at least demonstrate a common pattern of development

Parts of the body with similar structure (homologous)

BatWhaleCatHuman

Similar patterns of embryonic development (homologous)

BirdReptileSwineHuman

Yes, you had a tail as an embryo!

Homologous Development – actual photos of embryos

BirdReptile Rabbit Human

Biochemical similarities – DNA and Proteins

The ability to analyze individual biological molecules (DNA and proteins) has provided evidence for biochemical similarities

Methods of Change

Jean Baptiste Larmarck

French naturalist and evolutionary theorist

1744-1829 Proposed the

inheritance of acquired characteristics

Based on an “inner need” to change

Larmarck’s theory

His theory was disproved

Charles Darwin and Natural Selection (1859)

Naturalist on the HMS Beagle

Charles Darwin and Natural Selection (1859)

Exploration of South America (3 ½ years)

Visited the Galapagos Islands

Darwin’s theory of Natural Selection

1. Living things increase in number geometrically (overproduction)

2. There is no net increase in the number of individuals over a long period of time

Spider eggs: Many more produced than will survive

Darwin’s theory of Natural Selection

3. A “struggle for existence” since not all individuals can survive

4. No two individuals exactly alike (variation)

Darwin’s theory of Natural Selection

5. In the struggle for existence, those variations which are better adapted to their environment leave behind them proportionately more offspring than those less adapted

“Survival of the Fittest”

A Modern Perspective

1. Mutation – a sudden change in the genetic material (a source of variation)

Example: The DNA of one bacteria changes (becomes mutated), allowing it to become resistant to an antibiotic. It survives long enough to reproduce. Each succeeding generation has the mutated copy and is resistant to the antibiotic.

A Modern Perspective

2. Recombination of genes within a population (sexual reproduction)

Provides new combinations for natural selection to try.

Shows how the percentage of a gene in a population can change.

A Modern Perspective

3. Isolation – separation of a population from others of the same kind (species)

Prevents recombination of genes Species become different overtime Example: A species of primrose existed together where the

Promontory Range (Northern Utah) now exists. When the range lifted up, it isolated two groups. Both became different as they adapted to the different environments on either side of the range. They have become so different they can no longer reproduce.

A Modern Perspective

4. Natural Selection – certain traits give an adaptive advantage to organisms and they leave behind more offspring

They survive long enough to reproduce and pass on their genetic information

INDIVIDUALS DO NOT EVOLVE . . .POPULATIONS EVOLVE OVER TIME

Species

A group of individuals that LOOK similar and are capable of producing FERTILE offspring in the natural environment.

Population

All of the members of the same SPECIES that live in particular AREA at the same TIME.

Variation in a population

Bell Curve - The distribution of traits (Average is the middle.)

Mode - The number that occurs most often (High pt.)

Range - The lowest number to the highest number

Sexual Selection

Preferential choice of a MATE based on the presence of a specific trait

Speciation

The formation of new SPECIES

Isolation

Separation of a formerly successful BREEDING population

Geographic Isolation

Separated PHYSICALLY from each other

Reproductive Isolation

Can no longer produce FERTILE offspring

Extinction

When an entire SPECIES dies off.

Gene pool

The collection of GENES for all of the traits in a POPULATION

Hardy-Weinberg Principle

Genetic Equilibrium – no CHANGE in the gene pool

Conditions that must exist for genetic equilibrium

1. No MUTATION 2. No MIGRATION3. Large POPULATION 4. Random MATING 5. No NATURAL SELECTION

Natural Selection

Three types of selection1. Stabilizing Selection2. Directional Selection3. Disruptive Selection

Stabilizing Selection

Individuals with the AVERAGE form have the ADVANTAGE Example – lizards that are small are

not fast enough to avoid predators; lizards that are large cannot hide easily from predators; those of average size are both fast enough to get away from predators and small enough to hide – giving them the selective advantage.

Directional Selection

Individuals with one of the EXTREME forms have the ADVANTAGE Example – Peppermoth in Great Britain

during the industrial revolution – “melanistic” (dark colored) moths had the selective advantage after trees where covered in coal soot. After air quality improved, the selection advantage returned to the lighter colored moths.

Directional Selection Peppermoth – find two moths per

picture

As the ants dig deeper, anteaters with longer tongues have the adaptive advantage – survive to reproduce.

Disruptive Selection

Individuals with either of the EXTREME forms have the ADVANTAGE Example: a shellfish living in shallow ocean water

is preyed upon by a bird. Originally those with the neutral color (sand colored) had the advantage because they were camouflaged in the sand. As the birds fed on the shellfish and left their feces behind in the water, the ocean floor became white in color. Those shellfish that were sand colored are now easily found while the lighter colored shellfish are able to blend in, as are the darker colored shellfish if they are found on the darker rocks.

How have crops and livestock changed over the last 50 years?

In producing better livestock or crops, what are some examples of traits for which producers select?

Then

Now

Then

Now

Then

Now

Then

Now

Then

Removing Seeds

Now

Seedless

Then

Dehorning

Now

Polled

Natural Selection

an organisms’ ability to SURVIVE and pass on its GENETIC information to its offspring.

Selective Breeding

Also known as Artificial Selection Human control over organisms

passing on their genetic information. Human determination of those crops

and livestock allowed to reproduce Based on desired traits

Selective Breeding

In what ways is selective breeding similar to natural selection?

In what ways is it different?

Archeozoic Era

Oldest known rocks and fossils Animals without backbones

Jelly-fish, worms, sponges Bacteria and blue-green algae

Paleozoic Era

Estimated from 248-550 million years ago

Animals: Fish, amphibians, and insects

Plants: Algae and simple plants; first conifers

Mesozoic Era

Estimated from 65-248 million years ago

Age of the Dinosaurs Animals: Reptiles and birds Plants: Conifers and first flowering

plants

Cenozoic Era

Estimated from present to 65 million years ago

Age of the Mammals Animals: Mammals and birds Plants: Flowering plants