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Chapter 5 Evolution and Biodiversity: Origins, Niches, and Adaptation.

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Presentation on theme: "Chapter 5 Evolution and Biodiversity: Origins, Niches, and Adaptation."— Presentation transcript:

1 Chapter 5 Evolution and Biodiversity: Origins, Niches, and Adaptation

2 The Origin of Life How did life emerge on Earth? Chemical analysis and radioactive elements in rocks and fossils Simple inorganic compounds formed amino acids (proteins), simple sugars (carbs) and DNA/RNA

3 Most widely-accepted hypothesis Organic molecules needed for life came from inorganic chemicals in the Earths atmosphere -energy from lightning -heat from volcanoes -intense UV light -other forms of solar radiation

4 Scientific Experiments Since 1953 Placed mixtures of gases (in early atmosphere) into closed containers Subjected gases to sparks (lightning) and heat Building blocks (necessary for life) formed

5 Electrical sparks simulating lighting provide energy to synthesize organic compounds Sample for chemical analysis Cooled water containing organic compounds Cold water Condenser Electrode Water vapor H2OH2O CH 4 CO 2 N2N2 NH 3 H2H2 H2OH2O

6 Are there other possibilities? Organic molecules formed from… 1.Dust particles in space that reached earth on meteorites or comets 2.Deep within the earth 3.Hydrothermal vents (cracks in ocean floor, lead to chambers of molten rock)

7 REGARDLESS… Organic molecules accumulated and underwent chemical reactions for several hundred million years Led to formation of proteins, RNA, and other polymers that formed protocells Protocells could take up materials from environment, grow, and divide

8 Earth Developed in 2 Phases 1.Chemical evolution: organic molecules and chemical reactions to form protocells -1 billion years 1.Biological Evolution: single-celled prokaryotes single-celled eukaryotes multicellular organisms -3.8 billion years

9 Formation of the earths early crust and atmosphere Small organic molecules form in the seas Large organic molecules form in the seas First protocells form in the seas Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas Multicellular organisms form, first in the seas and later on land © 2004 Brooks/Cole – Thomson Learning Chemical Evolution Biological Evolution

10 How do we know what organisms lived in the past? Fossils!: mineralized or petrified replicas of skeletons, bones, teeth, shells, seeds, etc. 1.Physical evidence of organisms 2.Internal structures Fossil record is incomplete! We have 1% of species believed to have ever lived!

11 What is Evolution? Evolution: The change in a populations genetic makeup (gene pool) through successive generations Theory of Evolution: all species developed from earlier, ancestral species

12 Macro- and Microevolution Microevolution: small genetic changes that occur in a population Macroevolution: long-term, large-scale evolutionary changes through which… 1. new species are formed from ancestral species 2. other species are lost through extinction

13 Remember… Genetic information in chromosomes is contained in DNA Genes (on chromosomes) represent certain traits that may be passed to offspring Gene pool: set of all genes in individuals of a population Alleles: different forms of a gene (dominant or recessive)

14 Mutations Genetic variability originates through mutation: random changes in the DNA in a cell. Mutations happen in two ways: 1.DNA is exposed to radioactivity, X-rays, mutagens 2.Random mistakes when DNA is copied (cell division) Sometimes, mutations are beneficial

15 Microevolution Microevolution: change in a populations gene pool over time Summary of microevolution: genes mutate, individuals are selected, populations evolve

16 Natural Selection Occurs when individuals have traits that increase their chances of survival Needs 3 conditions: 1.Natural variability for a trait 2.Trait must be heritable 3.Must lead to differential reproduction (individuals with trait leave more offspring than individuals without trait)

17 Lets think about the moths again… 1.Variability: 2 color forms 2. Heritability: color form was genetically- based 3. Differential reproduction: greater survival and reproduction by one color

18 When environment changes… Population may: 1.Adapt to new conditions through natural selection 2.Migrate to an area with better conditions 3. Become extinct

19 3 Types of Natural Selection 1.Directional: changing environmental conditions select individuals who are not the norm so that their type makes up more of the population (it pays to be different) 2.Stabilizing: gets rid of individuals on both extremes (it pays to be average) 3.Diversifying: favors individuals with uncommon traits and reduces average individuals (it does not pay to be normal)

20 Natural selection New averagePrevious average Number of individuals Coloration of snails Proportion of light-colored snails in population increases Number of individuals Snail coloration best adapted to conditions Average Coloration of snails Average shifts Directional Natural Selection

21 Coloration of snails Light snails eliminated Dark snails eliminated Number of individuals Coloration of snails Snails with extreme coloration are eliminated Number of individuals Average remains the same, but the number of individuals with intermediate coloration increases Natural selection Stabilizing Natural Selection

22 Number of individuals with light and dark coloration increases, and the number with intermediate coloration decreases Coloration of snails Number of individuals Snails with light and dark colors dominate Coloration of snails Number of individuals Light coloration is favored Dark coloration is favored Intermediate-colored snails are selected against Natural selection Diversifying Natural Selection

23 Coevolution Changes in the gene pool of one species leads to changes in gene pool of the other Example: plants evolve defenses (camouflage, thorns, poison) effective against herbivores Herbivores evolve immunity against these traits

24 Ecological Niches Niche: role of a species in an ecosystem (like an occupation) Habitat: physical location (like an address) 2 types of niches: 1.Fundamental niche: potential and theoretical niche (without competition, etc) 2.Realized niche: actual niche

25 How do new species evolve? Speciation: two species arise from one Geographic isolation: groups of the same population become physically separated and undergo different evolution Ex. mountain range, volcano, earthquake Leads to reproductive isolation

26 Early fox population separates Adapted to heat through lightweight fur and long ears, legs, and nose, Which give off more heat. Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Gray Fox Arctic Fox Different environmental conditions lead to evolution into two different species. Southern population Northern population

27 EURASIA AFRICA SOUTH AMERICA INDIA 135 million years ago Present 65 million years ago 225 million years ago 120°80°0° 120° 80° 40° 120° GONDWANALAND 120° LAURASIA PANGAEA ANTARCTICA AUSTRALIA NORTH AMERICA MADA- GASCAR MADA- GASCAR

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