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History of Life on Earth

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Presentation on theme: "History of Life on Earth"— Presentation transcript:

1 History of Life on Earth
Chapter 12

2 The Age of the Earth 4.5 billion years old
Radiometric dating Radioactive isotopes break down over time Half-life – time it takes for half of amount to decay Using this can estimate age of earth Non-living chemicals reacted and produced organic molecules Combination of chemicals and energy from lightning/heat/Sun’s UV created organic molecules 2 Theories about how

3 Primordial Soup Oceans filled with organic molecules
Sparks simulate lightning Amino acids, fatty acids. And other hydrocarbons formed 1 problem: no ozone to protect from UV, certain compounds couldn’t have existed

4 Gases from undersea volcanoes trapped in bubbles that protect them from UV and concentrate them
Reactions happen faster Bubbles rise, burst, release compounds Energy from UV and lightning creates more reactions Complex organic molecules fall into ocean and start again Bubble Model

5 Precursor of 1st Cells Molecules of life can arise from simple chemistry RNA can be made in lab RNA believed to be 1st self-copying information storing molecule Makes proteins and changes from generation to generation; acts as an enzyme

6 These are steps toward cellular organization
Microspheres Amino acid chains form droplets in water Coacervate Droplet made of different kinds of molecules like amino acids and sugars These are steps toward cellular organization Microspheres last longer and longer and bring other molecules in

7 Origin of Heredity DNA came after RNA RNA catalyzed early proteins
Many believe RNA was brought into microsphere and could pass traits on But how DNA, RNA, and hereditary mechanisms first developed is still not known

8 12.2 The Evolution of Cellular Life: Prokaryotes
Fossil preserved or mineralized remains or imprints of an organism that lived long ago Oldest (2.5 billion years old) photosynthetic prokaryotes - cyanobacteria Created oxygen but took millions of years to build up to current amount

9 Two Groups of Bacteria Split Very Early
Eubacteria Peptidoglycan in cell walls Many cause disease and decay Archaebacteria No peptidoglycan Unique lipids in cell membrane Believed to resemble ancient archaebacteria

10 Evolution of Eukaryotes
1.5 bya first eukaryotes showed up Larger; internal membranes; DNA in nucleus Mitochondria in almost all Chloroplasts in plants and protists

11 Endosymbiosis Theory states bacteria entered large cells as parasites or undigested prey Begin to live inside host and performed cellular respiration or photosynthesis Mitochondria – descendents of symbiotic, aerobic eubacteria Chloroplasts – descendents of symbiotic, photosynthetic eubacteria

12 Support for Endosymbiosis
Size and Structure Mitochondria like eubacteria Chloroplasts like cyanobacteria Genetic Material Circular DNA similar to bacteria is different than hosts DNA Ribosomes Similar in size to those of bacteria Reproduction Simple fission independent of host

13 Multicellularity All living things are broken into 6 kingdoms
Eubacteria, Archaebacteria, Protista, Fungi, Plants, Animals Eubacteria and Archaebacteria oldest; single celled prokaryotes Protista – first eukaryotic kingdom, multicellular and unicellular All other eukaryotes, fungi, plants, and animals, came later and all came from protists

14 Unicellular is very successful
Almost every cell you can see is multicellular


16 Origins of Modern Organisms
Cambrian Explosion Most animal phyla originated during late Precambrian and early Cambrian periods Great evolutionary expansion Many unusual marine organisms appear that have no living relatives

17 Burgess Shale 1909 geological formation in Canada found
Ordovician Period – 505 mya – 438 mya Trilobites – extinct 250 mya

18 Burgess Shale

19 Mass Extinctions Large number of species become extinct
5 Major extinctions 440 mya 360 mya 245 mya – 96% of all species 210 mya 65 mya – 2/3 of all land species Today? Human activity might be causing another ½ of rainforests destroyed Keep up our current rate 22% to 47% of plants gone 2,000 of the 9,000 birds


21 12.3 Life Invaded Land Ozone Layer
Life evolved protected in oceans from dangerous UV rays from Sun No life on land during Cambrian period 2.5 bya photosynthesis puts O2 into air which reacts and forms Ozone, O3 Blocks UV Eventually enough to make it safe to live on land

22 Plants and Fungi on Land
1st organisms on land were probably a combination of plants and fungi; 430 mya Plants can make nutrients by photosynthesis Fungi can absorb minerals from rock Together called mycorrhizae, these exist today Mutualism – 2 species live together and both benefit

23 Theory of Evolution Chapter 13

24 13.1 The Theory of Evolution by Natural Selection
Before Darwin most people believed each species was a divine creation existing as it was when it was created But why were there fossils of unknown organisms?

25 Jean Baptiste Lamarck 1809 WRONG!!
Features of organisms change during life and are passed on to offspring Giraffe stretches neck to reach leaves, offspring have longer necks WRONG!!

26 And now for Darwin Charles Darwin was from a wealthy family
Studied medicine but became a minister (though he never became ordained) In 1831 Darwin went on a voyage on the HMS Beagle as a naturalist Galapagos Islands – plants and animals resembled those of the coast of South America

27 Darwin believed the organisms arrived from the coast and changed once they were there
Called this “descent with modification” which would become known as evolution Most famous were the finches and the tortoises He studied the data he collected for many years

28 Things That Affected Darwin
Thomas Malthus essay 1798 Human population was increasing faster than its food source Unchecked populations will grow geometrically Humans are checked by disease, war, & famine Charles Lyell book Principles of Geology Surface of Earth changed over time

29 Populations are all of the individuals of a species that live in a specific geographical area and can interbreed Darwin believed Malthus’s idea of unchecked population growth applied to all species “Individuals that have physical or behavioral traits that better suit their environment are more likely to survive and will reproduce more successfully than those that do not have such traits”

30 Evolution By Natural Selection
Natural Selection – Number of individuals with favorable characteristics that are inherited will increase Adaptations are inherited traits that become common because it produces a selective advantage

31 Publication of Darwin’s Work
1831 – Beagle voyage 1844 – very low public opinion of evolution 1859 – Another scientist, Alfred Russel Wallace, writes Darwin asking for help to publish his work that describes natural selection!! Darwin publishes his work and people aren’t happy to hear they are “related to apes”

32 Major Points of Theory Inherited variation exists within the genes of every population or species In environments, some individuals are better suited and have more offspring Beneficial traits spread Evidence that living species evolved from extinct organisms

33 UPDATE Now know genes are responsible for inherited traits
Natural selection causes the frequency of certain alleles in a population to increase or decrease over time

34 Species Formation Reproductive Isolation
2 populations of the same species do not breed with each other due to geographic separation, difference in mating periods, or other barriers Eventually they may not be able to breed with each other Kaibab squirrel and Abert squirrel

35 Tempo of Evolution Gradualism Punctuated Equilibrium
Slow/gradual process of changing that occurs continuously Punctuated Equilibrium Large changes that occur quickly

36 13.2 Evidence of Evolution Fossils
Many intermediate life forms have been found in fossils Not complete Certain environments are better for forming fossils Animals that live in areas that are not good for fossils are missing Studied by paleontologists

37 Anatomy and development
Comparisons can show similarities Vestigial structures Structures that have no use or have a less important function than they do in other related organisms Whale’s hind limbs Humans appendix

38 Vestigial Structures

39 Homologous Structures
Share a common ancestry Similar structure in different organisms Development of Embryos Believe you can see evolutionary history At some point all vertebrates have a tail, buds that become limbs, and pharyngeal pouches

40 Embryology

41 Biological Molecules Proteins DNA sequences
Smaller differences between closely related and larger between more distantly related DNA sequences Similar to relationships predicted by biologists

42 13.3 Examples of Evolution Factors in Natural Selection
All populations have genetic variation The environment presents challenges to successful reproduction Individuals tend to produce more offspring than the environment can support Better suited individuals leave more offspring

43 Example of Natural Selection
Tuberculosis (TB) kills more adults than any other infectious disease Antibiotics introduced in 50s now don’t work because bacteria are resistant Mutation in some bacteria made it resistant so it survived and passed on genes and becomes more common in population

44 Evolution in Darwin’s Finches
Darwin collected 31 specimens from 3 islands 9 distinct species all similar except for bills Large bills fed on seeds Small bills ate insects

45 Formation of New Species
Divergence – accumulation of differences between groups Speciation – process by which a new species forms Subspecies – populations of the same species that differ genetically because of adaptations to different living conditions First step of speciation

46 Subspecies

47 Maintaining New Species
When subspecies become different enough a reproductive barrier may form Geographic isolation Different reproduction times Physical differences Offspring not fertile

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