UNIT 3 Chapter 4 Evolution and Biodiversity The 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!

Background for Evolution from Biology 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

Evolution cont. 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

Genetic Diversity leads to Evolution 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?

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

What is coevolution?

Limits of adaptation through Natural Selection 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. Population’s GENE POOL RATE OF REPRODUCTION

Evolution Myths 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

How did each event affect Evolution? Tectonic plates Volcanoes Earthquakes Climate change Asteroids

Fundamental vs. Realized Niches 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!

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

Speciation- creation of a new species Most species take thousands-millions of years to evolve and create new species. What about fleas, ticks, roaches?

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

Speciation occurs due to: 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

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.

Species and families experiencing mass extinction Bar width represents relative number of living species Millions of years ago Era Period Extinction Current extinction crisis caused by human activities. Many species are expected to become extinct within the next 50–100 years. Quaternary Today Cenozoic Tertiary Extinction 65 Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Cretaceous Mesozoic Jurassic Extinction Triassic: 35% of animal families, including many reptiles and marine mollusks. 180 Triassic Extinction Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. 250 Permian Carboniferous Extinction 345 Figure 4.12 Fossils and radioactive dating indicate that five major mass extinctions (indicated by arrows) have taken place over the past 500 million years. Mass extinctions leave many organism roles (niches) unoccupied and create new niches. Each mass extinction has been followed by periods of recovery (represented by the wedge shapes) called adaptive radiations. During these periods, which last 10 million years or longer, new species evolve to fill new or vacated niches. Many scientists say that we are now in the midst of a sixth mass extinction, caused primarily by human activities. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites. Devonian Paleozoic Silurian Ordovician Extinction 500 Ordovician: 50% of animal families, including many trilobites. Cambrian Fig. 4-12, p. 93

Natural Selection takes a LONG time… 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

Genetic Engineering 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: Genetically Modified Organisms (GMO) GMOs use recombinant DNA genes or portions of genes from different organisms. Figure 4-14

Genetic Engineering Genetically modified organisms (GMOs)/transgenic organisms are the results of this gene splicing. Glowing tobacco http://upload.wikimedia.org/wikipedia/en/8/80/Glowi ng_tobacco_plant.jpg

Do you agree with cloning? Cloning plants, animals, humans, pets? Video of golden retriever cloned insert!!!