Origins of Biological Diversity

Evolution Part 2

Artificial vs. Natural SelectionArtificial Selection – selective breeding

of domesticated plants and animals to produce offspring with traits valuable to humans.

• Humans choose which traits are more common.

• Example – Dog Breeding (for temperament)

Natural Selection – Nature “selects” and favors traits more suitable for their particular environment.

• Result? Evolutionary adaptation to the environment.

Darwin’s Finches – The Making of New

Species • 13 species of Finches are unique to the

Galapagos Islands!

• All 13 species resemble the mainland species

• All 13 different species of finches have different beaks…result of Natural Selection!

• Why might they have different beaks?

Mainland

Why might Darwin’s Finches beaks look different?

• Hint: Galapagos is made of many different islands…each with different environments!

Darwin’s Observations: 4 Steps Leading to Natural Selection

1. Overproduction of Offspring – species produce more offspring than the environment can support

2. Leads to a “Struggle for Existence”

3. Many Variations within a population! – (def.) Differences among members of the

same species

4. Individuals with ‘best suited’ traits survive & have reproductive success = pass on their advantageous traits.

PesticidesNatural Selection in Action!

Using pesticides against insects can cause resistance over time!

Evolution (Part 2)

Microevolution & Speciation

Objectives

• Describe populations in terms of gene pools, gene frequencies, and genetic variations

• Identify types of genetic drift as random changes in population’s gene pools.

• Describe various ways speciation occurs.

Population & Natural Selection

Population – a group of individuals of the same species living at the same place at the same time

**Individuals don’t evolve…Populations Do!**

Example – Population of Deer in Berks County

Changes in Gene Pools…Microevolution!

• Microevolution is evolution on the smallest scale. – A generation – to – generation change

in the frequencies of alleles within a population.

– A population is the smallest level at which evolution can occur.

• Populations NOT undergoing change or evolving are said to be in Hardy-Weiberg Equilibrium. – Doesn’t really exist (almost impossible)

Microevolution is a Change within a Population’s Gene Pool

•Gene Pool – all of the alleles (forms of genes) in all the individuals of a population. – Where genetic variation (the

raw material of evolution) is stored.

•Allele Frequencies – how often an allele for a particular trait appears in a population.

Changes in Gene Pools are due to… Genetic Drift

Genetic Drift – a change in the gene pool of a population due to chance

1.Bottleneck Effect2.Founder Effect3.Gene Flow4.Mutations

Bottleneck Effect (type of genetic drift)

• Disasters (earthquakes, floods, droughts, and fires)

can drastically change the size and gene pool of a population.

• By chance, some alleles might be more frequently represented in survivors.

• Decreases genetic variation in populations.

Founder Effect(type of genetic drift)

• Occurs when a few individuals colonize an isolated new habitat (island, lake, etc.)

• The smaller the “founding colony” = the smaller the gene pool

• Reduces genetic variation

Gene Flow, Mutations, & Fitness

Gene Flow - Exchange of genes with another population– Occurs when individuals migrate between

populations

Mutation - A random change in an organism’s DNA

__________________________________________Fitness – The contribution that an individual

makes to the gene pool of the next generation compared the contributions of others.

Speciation

• (part 2 pp)

Come up with a definition for “species”

Hint: try to think about what makes these species different from one another.

15.1 Diversity of Life is Based on the Origin of New Species

Biological Species Concept

– Defines a species as a population or group of populations whose members have the ability to breed with one another and produce fertile offspring

Micro vs. Macroevolution

• Microevolution – smallest scale (populations evolved by gene pools changing by chance)

• Macroevolution – Dramatic! LONG!– Speciation

• The origin of different species (biological diversity)

– Extinction of Species– Evolution of new features

• Wings, webbed feet, etc.

What separates species & where do new species come from???

Reproductive Isolation- When a reproductive barrier keeps similar or closely related species from interbreeding!

– Timing– Behavior– Incompatibility– Infertile Offspring

Geographic Isolation & SpeciationIf Earth’s changes cause a population to become separated, the “splinter” populations may break off and follow their own evolutionary path and eventually become 2 or more different species.

Timing

Behavior

• Breeding opportunities occur at different times of the year…

• Different “dances”, communications, etc. initiate breeding.

Example: Spring vs. Fall

Frigate birds

World's 10 Most Bizarre Animal Mating Rituals

Ellen - Mating Rituals Mating Dance

Birds of Paradise

Incompatibility

Infertile Offspring

• Male and female reproductive organs are not able to come together.

• Male sperm & female eggs biologically/genetically can not become fertilized!

• Offspring (babies) are produced but are unable to reproduce. (genes can’t “live on”)

• Off

Speciation – gives rise to new species!

• Speciation: An Illustrated Introduction - YouTube

The Fossil Record Provides Evidence to Life’s History

• Fossils form when organisms are buried in sedimentary rock or other material and remains are preserved.

– Petrified (turned to stone)– Impressions (footprints, dung etc.)– Entire organisms preserved in ice (wooly

mammoth)– Amber (tree sap preserves insects)

Punctuated EquilibriumIn the fossil record we notice that:

• Species can appear abruptly

• Species can remain unchanged for long periods of time

• Species can disappear as quickly as they showed up

Punctuated Equilibrium – Long periods of little change (equilibrium) are broken (punctuated) by shorter times of rapid change/speciation.

Wooly Mammoth & Other Fossil Videos

Mammoth in Siberia

Geologic Time ScaleOrganizes Earth’s history into 4 distinct Eras:

• Boundaries between eras are characterized by major changes & mass extinctions

1. Precambrian (oldest)2. Paleozoic3. Mesozoic4. Cenozoic (most recent)

• T-Rex (extinct 65 million years ago)

• Irish Deer (extinct 7,700 years ago)

• Thylacine Tasmanian Tiger (extinct 1936)

• Quagga: ½ horse ½ zebra (extinct 1883)

Dating FossilsScientists can only study fossils if they know

their age!

By using the layered “rock strata” scientists can determine the general age of each fossil

based on which layer it was found in. (Example- Wallpaper)

Youngest

Oldest

Radiometric Dating

• Method used to determine the age of rocks and fossils based on the amount of radioactive isotopes in the object.

• An isotopes half-life is the time (years) it takes for 50% (half) of an original sample to decay.

• Isotope Half-Lives are unaffected by temp., pressure, etc.

Uranium-238 (half-life = 4.5 billion yrs.)

Carbon-14 (5,730 yrs.) Plutonium 239 (24,000 yrs.)

video:How Does Radiocarbon Dating Work? - Instant Egghead #28 - YouTube

Quick Demonstration

• How long does it take to for half of this same to decay (be lost)??

• WATCH THE CLOCK!!!

Activity: Understanding Half-Life

• You will be given a 8 pieces of paper and a “trash” cup.

• You will be asked to remove ½ of the paper you have in your hand every 30 seconds.

• When you remove ½ the paper…put it into the trash cup and assume it is gone forever!

• After each time you remove paper…write down how many pieces of paper remain in your hand and the time elapsed on the data table.

• Do not talk…just follow directions!!!!