UNIT 3 Chapter 4

Evolution and BiodiversityThe Earth is 6 billion years old.

Life is 3.7 billion years old.

ORIGINS OF LIFE 1 billion years of chemical change to form the

first cells, followed by about 3.7 billion years of biological change.

Figure 4-2

What factors make EARTH a perfect place for life to exist?

Temperature range Orbit distance from sun Rotation Size and gravitational mass Ozone Diversity which sustains life!

Evolution is the change in a population’s genetic makeup over time.

All species descend from earlier, ancestral species- theory of evolution

Can species evolve in one generation?

Darwin video

Background for Evolution from Biology

Microevolution describes the small genetic changes that occur in a population over time.◦ Over time, a population’s gene pool changes when

mutations in DNA molecules are passed on to offspring. There may be several different forms (alleles) of a single gene. Example: Alleles for eye color might be B (brown) and

b (blue) Homozygous vs. heterozygous Genotype vs. phenotype Dominant vs. recessive

Evolution cont.

◦ Sexual reproduction leads to random recombination of alleles from individual to individual. Crossing over Recombination

◦ Mutations causes genetic variability in populations due to random changes in structure/number of DNA molecules in a cell. Errors in transcription, translation, or replication

◦ Exposure to radiation (x-rays, UV light, radioactivity, mutagens (specific chemicals) can cause genetic variations

◦ Are all mutations harmful?

Genetic Diversity leads to Evolution

Genetic variability◦ Different traits to exist in the population ◦ Ex. Fur color

Traits must be heritable◦ Fur color depends on parents fur color

Trait must lead to Differential reproduction ◦ Trait allows those individuals to have more

reproductive success

◦ Video

In order for evolution to occur by natural selection there must be…

What is coevolution?

Limits of adaptation through Natural Selection

Population’s GENE POOL

RATE OF REPRODUCTION

The only genetic traits that can be selected for are those already in the gene pool.

Genetically diverse species that reproduce quickly, can often adapt quickly.

Populations that reproduce slowly take a long time to adapt through natural selection.

Survival of the fittest= the strongest survive

Organisms develop through the traits they NEED

Evolution follows a plan of nature to create the perfect species

Evolution Myths

Tectonic plates Volcanoes Earthquakes Climate change Asteroids

How did each event affect Evolution?

The niche includes the members’ adaptations; its range of tolerance for physical and chemical conditions, its interactions with other components of the ecosystem, and its role in energy flow and matter recycling.◦ The fundamental niche is the full potential range of

conditions and resources a species could potentially use.

◦ Its realized niche is the part of the potential niche that allows a species to survive and avoid competition with other species for the same resources.

◦ Video example insert!

Fundamental vs. Realized Niches

Generalist vs. Specialist Species

Broad Niches Specific niches

Specialized Feeding Niches

Resource partitioning reduces competition and allows sharing of limited resources.

Rainforest and specialist species

Most species take thousands-millions of years to evolve and create new species.

What about fleas, ticks, roaches?

Speciation- creation of a new species

Evolutionary Divergence

Each species has a beak specialized to take advantage of certain types of food resource.

Hybridization Gene Swapping Isolation

Geographic isolation- physical separation for long time periods.

Reproductive isolation-The gene pools are so changed that members become so different in genetic makeup that they cannot produce fertile offspring.

Behavioral isolation- individual doesn’t pick up mating cue

Speciation occurs due to:

Extinction: Lights Out Extinction occurs

when the population cannot adapt to changing environmental conditions.

The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate.

Fig. 4-12, p. 93

Tertiary

Bar width represents relative number of living speciesEra Period

Species and families experiencing

mass extinctionMillions ofyears ago

Ordovician: 50% of animal families, including many trilobites.

Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.

500

345

Cambrian

Ordovician

Silurian

Devonian

Extinction

Extinction

Pale

ozoi

cM

esoz

oic

Ceno

zoic

Triassic: 35% of animal families, including many reptiles and marine mollusks.Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.Carboniferous

Permian

Current extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including manyforaminiferans and mollusks.

Extinction

Extinction

Triassic

Jurassic

Cretaceous

250

180

65Extinction

ExtinctionQuaternary Today

Man has used artificial selection to change the genetic characteristics of populations for years.◦ We use selective breeding to obtain specific

desired traits. (plants, domestic animals) but this takes many generations also.

Humans have turned to the GENE REVOLUTION

Natural Selection takes a LONG time…

◦ Genetic engineering/gene splicing are techniques that isolate, modify, multiply and recombine genes from different organisms. Genes from different species that would never

interbreed in nature are being transferred to each other.

Genetic Engineering

Genetic Engineering: Genetically Modified Organisms (GMO)

GMOs use recombinant DNA genes or

portions of genes from different organisms.

Figure 4-14

◦ Genetically modified organisms (GMOs)/transgenic organisms are the results of this gene splicing. Glowing tobacco http://

upload.wikimedia.org/wikipedia/en/8/80/Glowing_tobacco_plant.jpg

Genetic Engineering

Cloning plants, animals, humans, pets?

Video of golden retriever cloned insert!!!

Do you agree with cloning?