Evidence for Evolution

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Biological diversity

The variety of living things

Evolutionary theory

Scientific explaination that is a collection of scientific facts, observations, and hypotheses that account for the diversity of life.

Evolution

( or change over time)

the process by which modern organism have descended from ancient organisms.

Theory

A well-supported testable explanation of phenomena that have occurred in the natural world.

The Big Bang theory

states that the universe began about 15 billion years ago as a dense tiny concentration of matter. That exploded violently. Energy and new forms of matter created by this explosion spread into space, gravitational attraction drew the matter together, forming stars and planets

Origin of Earth

Earth and other planets in this solar system develop 4.5 billion years ago.

From gases and dust orbiting the Sun gravity caused local accumulations of dust to form planets.

Solid matter was layered …

according to density. Heavy elements (iron) in the core, lighter elements formed a solid crust at Earth’s surface.

Radioactive decay …

deep in Earth heated the core

Magma

Molten rock inside Earth core that rose to the Earth’s surface (now lava)

Volcanic eruptions …

forced gases like nitrogen and water vapor out of the magma, that formed the atmosphere (no oxygen)

Earth condition 4.5 billion years ago

Surface covered with hot seas, kept by the molten Earth. Steam from sea formed huge clouds. Clouds precipitated to Earth in violent rainstorms, with lighting. On land active volcanoes spouted gas, steam and lava.

The early atmosphere and oceans contained … (Oparin model)

ammonia, water vapor, methane, and hydrogen.

What provided the energy to split molecules into atoms? (Oparin model)

Lighting, Earth’s heat, and Sun’s UV radition

The atoms bonded together to form … (Oparin model)

small organic compounds, carbon-containing molecules, characteristics of living things.

These molecules accumulated … (Oparin model)

in the ocean and formed a "primodial soup”, that after a long time formed globules of molecules that can reproduce and were the first life on Earth.

What did Miller and Urey do (hint: test)?

tested Oparin’s hypothesis.

Miller & Urey experiment

Filled a apparatus with water vapor, methane, hydrogen, and ammonia, passed an electric spark (lighting) through the mixture, and heated the mixture (earth’s heat). A liquid trap collected molecules formed in the apparatus.

After seven days …

they analyzed the liquid and found amino acids (building blocks of proteins) and other organic compounds.

The first cells

“protocells”

Probably resembled anaerobic bacteria cuz no oxygen in atmosphere. Probably lived off organic compounds from environment.

Cells capable of …

photosynthesis like cyanobacteria and other bacteria developed later about 3 billion year ago.

These organisms …

made their own food and gave off oxygen that gradually accumulated in the atmosphere and allowed for complex aerobic life (capable of using oxygen to obtain energy)

Fossil

Any preserved part or trace of an organism that once lived.

A fossil is formed when …

all or part an organism is buried before it can be eaten or decompose.

Most fossils are found in … (KNOW)

sedimentary rock

Sedimentary rock

forms from sediment (mud, silt, sand, and clay) that deposit in layers. High pressure on particles deep in sediment that become cemented together to form sandstone, limestone, shale and others.

Important requirements for fossilization …

are quick burial and presence of some hard parts. If not bacteria and other animals or processes that cause erosion can destroy it.

Meaning that not every organism …

becomes fossilized.

Imprints

Shallow, impressions in developing rock from soft body structures like feathers or leaves.

Molds (KNOW)

Deeper depressions in rock shaped like organism’s parts from teeth, shells, bones and other hard body parts.

Casts

formed from the mold being filled with another material due to the organism decomposing

Petrified wood

fossils that are the hard parts of an organism being gradually replaced by minerals.

Original Skeletal Material

hard parts of organisms that are preserved as the original material. Invertebrate shells (calcium carbonate, silica, chitin) or vertebrate bones (calcium phosphate).

Amber Entombment

Certain trees have a stick resin that small insects and other small organisms may be trapped in, which after burial may harden into amber.

Peat Bogs

Sphagnum moss forms thick “peat” in bogs called Peat Bogs that are very acidic prevents decomposition of organisms.

Tar Impregnation

Tar pits are excellent sites for fossilization.

Rancho La Brea in southern California yielded rich collections of vertebrate bone, wood, etc.

Small pits yield perfectly preserved insects and insect larvae.

Refrigeration

During the ice age animals (eg. mammoths) fell into crevasses in frozen terrain or became trapped in permanently frozen soil. Some have been discovered perfectly preserved.

Fewer then … of the animal species …

10%, are likely to be preserved as fossils.

Why are fossils so rare? KNOW

1. Very hard to find

2. No quick burial → broken down

3. Soft-bodied & lack hard parts

Very hard to find

Most fossils are buried under tons of rock and can only be discovered by chance when they are uncovered (usually by the natural forces of weathering and erosion). Plus they’re only found in sedimentary rock

1. No quick burial → broken down

If not rapidly buried after death, quickly broken down by scavengers (body parts spread apart) and bacterial decay.

Vast majority of living species are insects (1.5 million species 1 million are insects). Rarely preserved as fossils live on dry land and unlikely to be buried by sediment after death.

1. Soft-bodied & lack hard parts

Many organisms are soft-bodied and lack hard parts. Only preserved if isolated from oxygen immediately aft. death occurs when rapidly buried in fine-grained sediment in water. Only happens in rare, isolated environements

Relative dating

age of fossil determined by position in sedimentary rock. In undisturbed sedimentary rock, most recent fossils found in upper layers and older fossils in lower layers. Can determine relative age.

Flaw with relative dating

New surfaced fossils can go down deeper down with erosion. Possibly found with olders fossils and confuse the age of both fossils.

Absolute dating

Determaine exact age of fossils using radioactive isotopes (carbon-14) that decay into stable elements (nitrogen-14) at a constant rate (half-life)

Half life

Amount of time for specific radioisotope to decay half of its original mass (before half life). Carbon-14 half life is 5,730 years, uranium-238 = 4.5 billion yeras.

Carbon-14 is used to date fossils because …

it is replenished when alive but stop when die, 14C decays but 12C remain stable. Can determine age by comparing 14C and 12C (assuming 14C:12C living tissue today same as back then)

A fossil containing half 14C of living tissue would be …

5730 years old

A fossil with one-fourth 14C of living tissue would be

5370 × 2 = 11640 years old

Era KNOW

4 large units that is Earth’s 4.5 billion years.

Precambrian → Palezoic → Mesozoic → Cenozoic

Period KNOW

Era further subdived, Mesozoic periods are: Triassic → Jurassic → Cretaceuos

Epoch

Period further divided in smaller time spans

Paleontologist

Scientists who study fossils

Fossil record

Millions of fossils collect by paleontologist through many years, represents the collective history of Earth’s organisms.

Horse evolutionary history

60 millions years the horse evolved from “dawn horse” a dog-like, small, eyes forward, with a “dog paw” (4 toes), that lived in jungles to tall (2m), eyes on side, single toe with hoof, that are adapted to hard tall grass plains.

Fossil records also tells …

major changes in Earth’s climate and geography. Fossils of palm trees found in the Antarctic (climate was once warm). Fossil shark teeth found in Arizona (desserts of American Southwest once covered by ancient seas.

Embryos

Organisms in the early stages of development

Comparative embryology

The study that compares embryos of different species, found similarities that support the theory of evolution.

Species with embryo similarites share …

common genetic instructions for embryo development, and therefore share a common ancestor.

Example of comparative embryology

Vertebrates (animals with backbones) have genes active during early embryological development that are the shared heritage from a common ancestor.

The common ancestor of …

these diff. species had a particular sequence of genes (controlled early development) and has been been passed on to species that descended from it.

Fetus

Developed embryos, become more and more dissimilar caused by genes that have changed during evolution through mutations.

Why do embryos look similar? KNOW

Mutations that affect embryos are likely to be lethal. Organism with mutation dies as an embryo and genes are not passed on.

The genes that control embryo development …

remain relatively unchanged (is why embryos of diff. animals look alike).

Fetus are …

tougher so mutations that occur (useful or harmful) survive and reproduce and pass the changes to offsprings ( is why later development of related organisms begin to differentiate)

Homologous structures

Body parts with same basic structure, whether function is diff. or not.

Examples: Bat wing, human arm, and whale flipper

Homologous structures found in diff. organisms suggest …

that these organisms have a common ancestry.

Clumps of cells on diff. animal embryos that develop into limbs look …

quite similar, but embryo mature limbs grow into arms, wings, legs and flippers (different “form” and function)

Different forelimbs came from a …

series of evolutionary changes that altered the structure and appearance of the arm and leg bones of ancient animals.

Final structure of limbs of diff. species are …

adaptations that enable each species to be successful in their (different) environments.

Vestigial structures

body structures that have been reduced in size and seem to serve little or no purpose (once performed a useful function in ancestral forms). Homologous with larger useful structures found in other living organims.

Vestigial structures provide evidence for evolution because evolution involves …

the loss or reduction of structures who main function is no longer valuable often becoming smaller but never disappearing completely.

Examples of vestigial structures

Appendix (humans) = suggests ancestors had a functioning appendix and were herbivores.

Coccyx / tail bone (humans) = evolutionary ancestors had a tail supported by vertebrae

Hindlimbs (modern whales) = Evidence for evolution from four footed terrestrial ancestor.

Leg bones in snake, Ear muscles (human), horse splint bone in leg

Comparative biochemistry

Study of molecules that make up different living things.

Evidence from comparative biochemistry shows that …

All organisms, from bacteria to humans share biochemical details. More closely related = more closely related important chemical compounds resemble each other.

Example of comparative biochemistry 1

All organisms use DNA and/or RNA. Eukaryotes DNA same structure and replicates same way. RNAs of various species may act a little diff. but all have similar structure. Also ATP found in all living things

Example of comparative biochemistry 2

Cytochrome C = protein (4 aerobic cellular respiration).

Diff. A.A seq. 4 diff. species.

But # of DNA nucleotide (in gene 4 cytochrome c) diff. less btwn more closely related species compared to distantly related species

(humans & monkeys 1 N difference, humans & snake 14 N difference)