Chapter 5 and 6Evolution of Living Things &

History of Life on Earth

Sections 1-3 Pages 106-129Sections 1-3 Pages 136-153

Differences among Organisms• Adaptation: A characteristic

that helps an organism survive and reproduce in its environment. Adaptations may be physical or behaviors.

• Species: A group of organism that can mate with one another to produce fertile offspring. Groups of individuals of the same species living in the same place make up a population.

Do species change over time?• Evolution: The process in which inherited characteristics within a

population change over generations such that new species sometimes arise

Evidence of Changes over Time

• Fossils: remains or imprints of once living organisms– Usually formed from

complete organisms, parts of organisms, or a set of foot prints

• Fossil Record: organizes fossils by their estimated ages and physical similarities

Earth’s History as a Clock

Change over Time: Evidence of Ancestry

• Drawing ConnectionsScientists examine the fossil record to figure out the relationships between extinct and living organisms

Examining Organisms

• Evidence of whale evolution: using fossils to support the hypothesis

Comparing Organisms • Comparing skeletal structure: similar bones can be examined

in different animals to demonstrate a common ancestor • Comparing DNA: If species that have similar traits evolved

from a common ancestor , the species would have similar genetic code

How Does Evolution Happen?

• Charles Darwin: During a 5 year voyage, this 21 year old, traveled post college to study nature.

• On his journey aboard the Beagle, Darwin collected plant and animal samples. He visited the Galapagos Islands.

Darwin’s Finches

• Noticed the similarities between plants and animals on Galapagos and Ecuador (600 miles apart).

Darwin's Thinking

• Traits: a genetically determined characteristic

• Selective Breeding: The human practice of breeding animals or plants that have certain desired characteristics

Ideas about Population

• Darwin gained knowledge from Thomas Malthus’ book An Essay on the Principle of Population.

• Darwin reasoned that the offspring of survivors inherit traits that help the offspring survive in their environment.

Ideas about Earth

• Darwin began to think species could evolve over time.

• Darwin learned from Principles of Geology (Charles Lyell) that Earth had been formed by natural processes over a long period of time.

Darwin’s Theory of Natural Selection

• Darwin struggled for over 20 years with his ideas until Wallace mailed him a letter expressing similar ideas

• In 1859 Darwin published Origin of the Species by Means of Natural Selection in which he proposed the theory of evolution happens through a process that he called natural selection

Genetics and Evolution• Darwin lacked evidence for

parts of his theory• He could not prove how

variation occurred• Scientists today found that

variation happens as a result of differences of genes

• These changes occur whenever offspring are produced

• These changes allow the organism better ability to survive and reproduce, this is called selection

Changes in Population • Adaptation to Hunting:

example tusk less elephants • Insecticide Resistance:

insects can develop quick resistance because of their rapid reproduction of offspring, having a shorter generation time

• Competition for Mates:example bird species

Forming a New Species – Speciation

• Separation: usually begin when part of the population gets separated from the rest (mountain range, canyon, lake formation)

• Adaptation: over generation the separated group develops new traits

• Division: If the two groups are reunited (barrier removed) they are no longer the same species and can not reproduce with each other

Fossilized Organisms • A fossil is the remains or physical

evidence of an organism preserved by geological processes

• Fossils in rock: sometimes decaying organisms get quickly buried by sediment (rock), then the sediment becomes a rock. The harder parts of the animal (bones) become well preserved in this newly formed rock.

• Fossils in amber: Organisms (insects) get caught in soft sticky tree sap which hardens and preserves them.

Absolute Dating• The process of

establishing the age of an object by determining the number of years it has existed is called absolute dating.

Radiometric Dating• If you know the rate of decay for a

radioactive element, you can determine the absolute age of the rock.

• Based on a parent to daughter ratio, you can determine the absolute age, this process is called radiometric dating.

• A half life is the time that it takes one half of the radioactive sample to decay.

• After every half-life, the amount of parent material decreases by one-half.

½, ¼, 1/8, 1/16

Try this example: Carbon 14’s half-life is 5, 730 years. How old will the object containing this be when ¼, 1/8, 1/16, 1/32 of it’s Carbon 14 remains.

Geological Column• Used to help geologists,

they combine data from all the known undisturbed rock sequences around the world

• Geologists use the geological column to interpret rock sequences and to identify layers in puzzling rock sequences

Extinction

• The death of every member of the species.

• Can be caused by global change and/or change in ocean currents

Changing Earth• Pangaea: “All Earth” one

supercontinent breaking up

• Plate Tectonics: Continents/huge pieces of land moved slowly on plates

• Adaptation to slow change: organisms from the past present along with current organisms

Precambrian Time• Time from the formation of

the Earth, 4.6 billion years ago to about 543 million years ago.

• Violent events (volcanic eruptions) and harsh atmosphere.

• Simple chemicals may have reacted during these storms from the energy of radiation. Single celled organisms resulted (prokaryotes).

Precambrian Time• Photosynthesis and Oxygen-

Cyanobacteria used sunlight to make food over 3 billion years ago, and started to release Oxygen. Ozone layer began to form as a result.

• Multi cellular Organisms-A billion years after prokaryotes appeared Earth had eukaryotes (many celled organisms with a nucleus)

Paleozoic Era

• Marine life flourished• Land plants appeared• Amphibians and reptiles• Insects• Largest mass extinction

in Earth’s history….cause? Ocean currents?

Mesozoic Era

• Age of the Reptiles• Small mammals• Dinosaurs and birds• Extinction….cause?....

Global climate?

Cenozoic Era

• Age of Mammals• Mammals competed

with dinosaurs • Due to climate change…

mammals better suited for environment

Humans and other Primates• Primates – group of

mammals that include humans, apes, monkeys, and lemurs (opposable thumbs and binocular vision)

• Hominids- includes humans and other human like ancestors. The main difference is bipedalism “walking upright”

Hominids through Time• Early Hominids- similar to

humans more than apes. Oldest fossils in Africa- 6 to 7 millions years old.

• Australopithecines- Similar to apes, found in Africa. Had human like and ape like characteristics

• Global Hominids- Slender, more human like, larger and more complex brain, walked upright and used tools. (homo habilis and homo erectus)

Recent Hominids

• Neanderthals- about 400,000 years ago, extinction, reason unknown

• Early and Modern Humans- homo sapiens, first to create art

• Paleontologists will review their ideas about evolution of hominids

Comparison of Hominids Australopithecines Early Homo Homo sapiens

Bipedalism yes yes yes

Brains medium larger largest

Tools none some many

Art none none A lot

Known Locations Africa Several continents World wide

Brain Pops, Games, etc.• Darwin• Natural Selection• Primates• Human Evolution• http://exploringorigins.org/index.htmlGAMES!!!• http://

science.discovery.com/interactives/literacy/darwin/darwin.html• http://www.pbs.org/wgbh/nova/evolution/evolution-action.html• http://

www.mnh.si.edu/ete/ETE_Education&Outreach_Game.html