Chapter 15-17: Change Over Time Notes

Early History

• Probably very hot from meteorites hitting Earth

• Atmosphere lacked oxygen• Gases from volcanic eruptions–Water vapor, carbon dioxide, nitrogen,

methane, and ammonia– Helped form an early atmosphere

• Oldest rocks formed 3.9 billion years ago• Earth formed 4.6 billion years ago

Oparin’s Hypothesis

• Life began in the oceans

• Sun’s energy, lightning, and heat from Earth triggered chemical reactions

–Produced small organic molecules from elements in atmosphere

• Rain washed molecules into the oceans to make primordial soup

Miller and Urey• Simulated conditions of early

Earth in a lab• Mixed water vapor with

ammonia, methane, and hydrogen gases

• Sent an electric current through mixture then cooled it– Found amino acids, sugars, and

other small organic molecules

• Experiment supported Oparin’s hypothesis

• Earth may have cooled around 4.4 billion years ago

–Water in atmosphere condensed resulting in a lot of rainstorms for millions of years

• Scientists estimated life began in the oceans 3.9-3.4 billion years ago

Origin of Life

• Abiogenesis (spontaneous generation)

–Life comes from nonliving material

Francesco Redi (1668)

• Disproved spontaneous generation of larger organisms

–Nonliving material cannot produce life

–Did an experiment involving meat and maggots

Louis Pasteur (mid-1880’s)

• Disproved spontaneous generation of microorganisms– Completely isolated a culture medium with no

outside influence like spores or eggs• Boiled culture several times• Observed no living organisms appeared

• Biogenesis: living organisms come only from other living organisms

• Sidney Fox: heated solutions of amino acids to produce protocells (large, ordered structure enclosed by a membrane that carries out life activities)

Origin of Cells

• First cells probably prokaryotes (anaerobic): 2 billion years ago

• Unicellular

• Heterotrophs

• Archaebacteria

–Live in harsh environments (deep sea vents and hot springs)

• Development of photosynthesizing bacteria

–Released oxygen from water

–Oxygen turned into ozone by sun’s rays made ozone layer

Endosymbiont Theory• Proposed by Lynn Margulis in the 1960’s

• Eukaryotic cells evolved from prokaryotic cells through a symbiotic relationship

• Chloroplasts and mitochondria contain DNA similar to DNA in prokaryotes– Prokaryote ingested aerobic bacteria (produced

energy for the cell)– Over time the aerobes became mitochondria– Some prokaryotes also ingested cyanobacteria

(blue/green algae) that contain photosynthetic pigments

– Cyanobacteria became chloroplasts when ingested

Geologic Time Scale• Divisions based on

organisms that lived during that time

• Begins with the formation of earth

• Calendar of Earth’s history

• 4.6 billion years

• divided into eras and periods

–Precambrian: 87% of Earth’s history

• Paleozoic: Cambrian explosion of new diversity

–Largest mass extinction 90% of life disappeared

• Mesozoic: mammals 1st appeared and age of the dinosaurs

–Extinction of the dinosaurs and 2/3 of all living species

–Pangaea: 1 large land mass

•Was split apart due to plate tectonics: continually moving land masses

• Cenozoic: era in which we live in today

Mass Extinction

• entire groups of organisms disappear from the fossil record almost at once

1. Evidence shows that certain species have disappeared, or become _____.

2. We are currently living in the _____ era.

3. Humans of today would not be able to survive in Earth’s early atmosphere because it contained little or no ______.

Ch. 15-17 Bell Ringer #1:

Evolution• Thomas Malthus: proposed that the

human population grows faster than Earth’s food supply• Gradual change in populations

over time

• Proposed by Charles Darwin–Observed plant and animal life on the

Galapagos Islands (ex: finches, tortoises)–Wrote On the Origin of Species

• Species evolve, not individual organisms• Occurs by Natural Selection: “Survival of

the Fittest”–Process by which individuals that are

better adapted to their environment are more likely to survive and reproduce than other members of the same species

3 Factors that Affect Natural Selection

• Overproduction

•Species produce far more offspring than can survive

•May not be enough resources (food, water, living space)

• Competition•Members of a species must compete

with each other to survive•Does not usually involve direct physical

fighting (usually indirect)• Lack of finding food• Predation

• Variations– Differences between individuals of

the same species– Can make individuals better

adapted to their environment (more likely to survive and reproduce)

– Offspring may inherit helpful characteristics

– Environmental changes• Can lead to selection

– Genetic variation• Can result from the shuffling of

alleles during meiosis or mutations

• Over time natural selection can lead to change in populations– some individuals have differences that permit them to

adapt and increase their chances for survival– Organisms with favorable variations survive, reproduce,

and pass their variations to the next generation– Organisms lacking favorable variations less likely to

survive and reproduce– The ability to survive and reproduce in an environment

is an organism’s fitness.

Evidence for Evolution

Adaptations

• any variation that aids an organism’s chances of survival in its environment

–Develop over many generations

–Can be structural or behavioral

Mimicry• one species can resemble another species• Can provide protection from predators• Can look harmful or look like another harmful

species

Camouflage

• Allows species to blend in with their surroundings

• Used to avoid predators survive to reproduce

Physiological Adaptations• Changes in an organism’s metabolic processes– Bacterial antibiotic resistance – Resistance to pesticides• Used to kill harmful insects• Some insects have traits that protect them from the

pesticide and can survive• Surviving offspring inherit the pesticide protection• Pesticide becomes ineffective over several

generations

Fossils

• studied by paleontologists– Used to learn the history of life– Evidence of an organism that lived a long time

ago– 99% of species have become extinct

• Can analyze structures of ancient organisms

• Can also be used to find out about ancient climate and geography

Fossil Formation• Can form in many ways– Organisms die and become

buried in sediments (particles of soil and rock, mud, sand, or clay)

– Become compressed over time which hardens into rock

• Many found in sedimentary rock– Oldest fossils in the deepest

layers– Can show a gradual series of

changes in form of a species through layers of sediment

Types of Fossils• Petrified fossils: minerals replace

hard parts of an organism• Trace fossils: footprints, trials,

burrows• Molds: decayed organism leaving

an empty space• Casts: minerals fill spaces• Preserved remains• Hard parts: bones, teeth, shells,

leaves• Imprints• Amber: resin from trees• Tar pits

Relative Dating• Used to determine age of

fossils in layers of rock• Compares a fossil’s location

relative to other fossils in nearby rock layers

• Cannot tell actual age• Look at rock layers oldest

closer to the bottom• Diagram:

Radiometric Dating

• Used to determine specific age of rocks and fossils• Radioactive isotopes in rocks (decay

over time giving off radiation)• Half-life: decay rate of a radioactive

isotope

Homologous Structures

• Structural features with a common evolutionary origin

• Similarity in body parts of different organisms due to a common ancestor

• May differ in function but are similar in structure• Ex: human hand, bat wing, amphibian leg, bird

wing, whale forelimb

Analogous Structures

• Body parts that do not have a common evolutionary origin but are similar in function and appearance

• Structures with different anatomy but similar function

• Ex: flippers of dolphin, shark, and penguin, bird and insect wings

Vestigial Structures

• No current function presently but are similar to functional structures in related organisms

• No longer serves its original purpose but was useful to an ancestor

• Still inherited even though it is no longer needed• Ex: whale pelvic bone, snake leg bone, human

appendix and tail bone

Embryology• Embryo: earliest stage of

growth and development of plants and animals

• All embryos have similar anatomy

• Comparing early development of different organisms

• Proceed through similar stages of development

• Ex: fish, turtles, chickens, mice, humans all look the same

• Gill arches and tails

Biochemistry

• Cytochrome c sequence• Amino Acid sequence similarities• DNA Similarities– Inherited similar genes from a common ancestor– Compare the sequence of nitrogen bases in DNA of

different species to determine how closely related they are

– Can compare the order of amino acids in a protein to compare relatedness

Ch. 15-17 Bell Ringer #2:1. A human’s appendix and snake legs are

examples of ___.a. Vestigial organs c. Adaptation

b. Fitness d. Struggle for existence

2. Another phrase for natural selection is “____”.

3. What conditions could force organisms to compete in a struggle for existence?

Populations and Evolution

• Evolution occurs as a population’s genes change over time– All genes together in a large

gene pool: all of the alleles in a population’s genes

– Evolution occurs when there is a change in the gene pool• Mutations–Environmental or by

chance

• Genetic drift: the alteration of allelic frequencies by chance events

–Can affect small populations

• Movement in and out of a population

–Transporting genes (Gene flow: movement of genes in and out of the gene pool)

• 3 different types of natural selection that acts on variation

–Stabilizing selection

• Favors average individuals in a population

•Diagram:

• Directional selection

–Favors one of the extreme variations of a trait

–Diagram:

• Disruptive selection

– Individuals with either extreme of a traits variation are selected for

–Tends to eliminate the intermediate phenotypes

–Diagram:

Evolution of Species

• Species: group of organisms that look alike and can interbreed

• Speciation: the evolution of a new species– Members of similar populations can no longer

interbreed to produce fertile offspring– Changes in allele frequencies that can result in the

formation of a new species from a parent species– Ex: Darwin’s finches

• Creation of a new species– Form when a group of individuals remains

isolated from the rest of its species long enough to evolve different traits

– Isolation occurs when they are cut off from the rest of the species

• Geographic Isolation: physical barrier divides a population

–Bodies of water

–Volcanoes

–Mountain ranges

– Island formation

• Reproductive isolation: organisms can no longer mate and produce fertile offspring

–Influenced by different genetic material and behavior patterns

Patterns of Evolution

• Charles Darwin observed different species of finches

• Adaptive radiation– An ancestral species evolves into a variety of

different species to fit a number of different habitats

• Divergent evolution

–Species that once were similar to an ancestral species become distinct or different

–Populations change as they adapt to new/different environmental conditions

–Results in new species

• Convergent evolution

–Distantly related organisms evolve similar traits

–Occupy similar environments in different parts of the world

1. The combined genetic information of all members of a particular population is called a (an) _____.

2. Genetic drift is more likely to occur in ___.a. Large populations c. Small populations

b. Medium-sized populations d. One individual

3. What is the formation of a new species called?

Ch. 15-17 Bell Ringer #3: