chapter 15 and 16 (pgs 278-317) mrs. mcnamara biology biology reveals that common genetic sequences...

Chapter 15 and 16 (pgs 278-317) Mrs. McNamara

Biology

Living organisms can only come from other living organisms.

Life on earth most likely originated from non-living materials.

Biogenesis – Principle that says all living things come from other living things

We know this now…but we used to think:

Spontaneous Generation – Theory from the

early 1600’s stating that living things could also arise from nonliving things

(Example: Maggots appear on rotting meat)

The debate was solved by curious people who ask

questions!

Francesco Redi (1626-1697) Noticed adult flies producing ‘oval cases’ from which new flies eventually arose

1668 controlled experiment (supports biogenesis)

Louis Pasteur (1822-1895) Different experiment,

but same conclusion Modification of Lazzaro

Spallanzani’s experiment (monitors microorganismal growth)

Miller and Urey created an apparatus (1953) to mimic the early atmosphere of Earth.

A mixture of methane, ammonia, hydrogen, and water vapor was energized, then condensed

A ‘scum’ was extracted and found to contain AMINO ACIDS

Life comes from life, comes from life, comes from… ?

4.6 billion years ago – our planet was formed 3.9 billion years ago – oceans formed 3.5 billion years ago – we have evidence of life! FACT: The organisms that existed then

are different from those that live today. EVOLUTION – The slow, gradual change of a species

over time.

QUESTION: In science, when do we say that a hypothesis is proven?

Theory – the status of a hypothesis when it has been

supported by a large amount of evidence.

1. How old is the Earth?

2. Can organisms come from nothing? How do we know?

The fossil record documents the process of natural selection.

Geographic patterns of species distributions reflect their evolutionary histories.

Comparative anatomy and embryology reveal common evolutionary origins.

Molecular biology reveals that common genetic sequences link all life forms.

The Fossil Record Structural Similarities Vestigial Structures Embryonic Development Genetic Similarities

How do we know that life has changed over time?

What were organisms like millions of years ago?

FOSSIL-preserved remains of a long dead organism. Types:

Rock, molds (imprints), casts (rocklike model of the organism-reverse of imprints), amber, ice, bogs, bones, etc. Most living things never become fossils.

Their tissues and organs decay quickly after they die. To become a fossil, an organism must be preserved. There are several ways that this preservation can occur.

MOLD – A hollow impression of a once living organism.

CAST - solid mineral deposit that filled a mold, leaving a copy of the once living organism

WHOLE ANIMAL - an entire plant or animal encased and preserved in ice, sap, or another material

PERTIFIED - plant or animal tissue (organic)

replaced by minerals.

Ice… This baby mammoth was an early ancestor of the elephant. It has been extinct for almost 10,000 years. In March 1999, scientists found a fossil of a mammoth frozen in ice. The ice preserved parts of the body. Even some flesh and hair remained on the mammoth.

THE FOSSIL RECORD (a time scale for

the entire history of life on our planet) indicates that over time, organisms of increasing complexity appeared on earth Several MASS EXTINCTIONS-periods when

large numbers of species disappeared. Causes: drastic changes in the environment, volcanic

activity, meteors, drop in temperature, ash and dust in the atmosphere which doesn’t allow sun to pass through, etc.

Where are fossils usually found? Sedimentary Rock-rocks made up of layers of

sediments, or bits of clay, soil, sand, and other materials.

Sedimentary rocks usually forms in water. When an organism dies, its soft parts decay and its hard parts become buried in sediments. The sediments are pressed together by great pressure. Eventually, the sediments and bones form rocks. The outlines of the organisms are left in those rocks.

HOW CAN WE TELL HOW OLD THE FOSSIL IS?

Relative dating- fossils found in LOWER layers of rock are OLDER. process of dating fossils to

determine their age relative to other fossils.

Uses the LAW OF SUPERPOSITION-layers of rock that make up the earth’s crust, or soil were deposited on top of one another over time. Lowest level (a.k.a. STRATUM-layer of the

earth’s crust) is the oldest.

Actual Dating- process of dating fossils to obtain a more exact age. Uses Radiometric Dating- measure

the number of atoms of a radioactive element in a fossil sample. Use this number along with the element’s Half Life- rate at which it takes the radioactive element to decrease by ½.

BIOGEOGRAPHY-study of distribution of fossils and living organisms. Shows that new organisms arise in places where

similar organisms used to live.

Homologous Structures Similar features that originated in a shared

ancestor.

Different function but structurally similar (internally).

Example: penguin wing, alligator leg, bat wing, human arm---internal structure is similar, look different, different functions.

Result from: common ancestry.-show they are related.

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Homologous Structures

copyright cmassengale

Analogous Structures Identical functions, different structure

(internally).

Example: butterfly wings and bird wings…fly eye and human eye.

Results from: natural selection (similar environmental pressures) – does not show the species are related.

Vestigial Structures Structures useful to ancestor, but not useful

to modern organism. Example: tailbone, appendix, wisdom teeth, muscles

that wiggle your ears; snake and whale pelvic bones.

Organisms still contain genes that code for these…the genes give clues to evolutionary history.

Currently, these body parts are not perceived as useful…but this could change as we learn more.

Embryo Development Similarities in early

stages of embryonic development (conception to birth) among a variety of different species.

Suggest a common ancestor.

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Evidence for Evolution - Comparative Embryology

Similarities In Embryonic Development


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Chicken Turtle

Rat


Similarities in DNA The more closely related two organisms are,

the more similar the DNA sequences.

33 Similarities in DNA Sequence copyright cmassengale

1. Which structures show a close evolutionary relationship and are evidence of a common ancestor?

2. Name an example of a vestigial organ. Why do we have them?

3. Name the things we use as evidence of evolution.

Before Darwin, most people believed that all species had been created separately and were unchanging.

Observing geographic similarities and differences among fossils and living plants and animals, Darwin developed a theory of evolution.

French scientist (1744-1829)

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Inheritance of Acquired Characteristics Lamarck put forward the idea that traits would be changed/modified based on a conscious use or disuse, and that this modified trait would be passed on

WRONG!! No evidence for this!


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According to Lamarck, the earliest giraffes ate grass. When the grass died out, giraffes needed to find new food sources. They stretched their necks to reach the leaves on trees. As they stretched, their necks grew longer.

Lamark believed that the development of these ‘stretched neck traits’ could be passed to offspring.

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Clipped ears of dogs could be passed to offspring! copyright cmassengale

English scientist (1809-1882) 1831-sailed on the HMS Beagle. Sailed to the Galapagos Islands (off coast of

South America) and conducted many famous studies. Studied many types of finches (bird). Saw each was a bit different from the other, but

were also similar (maybe a common ancestor?). Also saw tortoises and iguanas living in different

areas were different depending on the food they ate.

Published The Origin of the Species to explain his findings (Theory of Natural Selection).

Darwin knew that traits are passed on, but he did not know how it occurred. Today, we know about DNA. With each new generation of a species, there is a new combination of genes.

Because of the similarities between the finch species, Darwin inferred that the finches shared a common ancestor and evolved over time.

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Evidence for Evolution – The Fossil Record


1. Summarize Lamarck’s theory.

2. Summarize Darwin’s theory.

3. Why was Lamarck incorrect?

Evolution occurs when the allele frequencies in a population change.

When three simple conditions are satisfied, evolution by natural selection is occurring.

Through natural selection, populations of organisms can become adapted to their environment.

A population can become better match to its environment through natural selection.

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NATURAL SELECTION: organisms with traits that make them better suited to the environment survive and have babies while others die. These favorable traits are passed to babies with favorable traits accumulating over generations.

Example: Clown fish, bats (echolocation), giraffes (long

neck), lion (sense of smell, ability to be quiet while stalking gazelle, etc).

1. Competition for resources (some get more, some get less – resources are limited)

2. Variation of traits (so some traits may be an advantage)

3. Reproduction (to pass the traits down).

Variation: differences in a trait from organism to organism within a population. Ex: different hair colors, pepper colors, pepper

sizes, skin color, etc.

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Fitness: Ability of an Individual To Survive & Reproduce

Individuals With Low Fitness Die Produce Few Offspring

Survival of the Fittest

AKA Natural Selection


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Adaptation: Inherited Characteristic That Increases an Organisms Chance for Survival Adaptations Can Be: Physical Speed, Camouflage, Claws, Quills, etc.

Behavioral Solitary, Herds, Packs, Activity, etc.


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Key Concept: In Artificial Selection, Nature Provided The Variation Among Different Organisms, And Humans Selected Those Variations That They Found Useful


57 copyright cmassengale

1. What 3 conditions must be met for evolution to occur via natural selection?

2. What is fitness? How can we tell if an animal is fit?

3. Are all traits adaptations?

Species are the basic units of biodiversity.

Speciation is the process by which one species splits into two distinct species that are reproductively isolated.

Isolation: 2 sets of genes are kept separate by either:

Geographic Isolation: 2 groups genetics are

kept apart because the members of the 2 populations are physically separated by barriers.

Examples of barriers: ocean, the grand canyon, rivers, mountains, etc.

Reproductive Isolation: 2 species are unable to produce fertile offspring together, no matter where they live. 2 Types:

1. Prezygotic Isolation:The sperm and egg are prevented from meeting.

Examples: different mating times, different mating behaviors, parts don’t fit together.

2. Postzygotic Isolation:The sperm and egg meet, but fertile offspring is not produced.

Examples: baby never develops, baby develops but dies early, or offspring is unable to produce offspring of its own (infertile).

Even though the 2 types of fruit flies can see each other, they don’t recognize the type that lives on the other fruit as a fly they can mate with. They will ignore each other.

An example is the American Toad and the Fowler's Toad. These species have been mated in laboratory settings, but mating does not happen in the wild because the American Toad mates early in the summer, and the Fowler's Toad mates in late summer.

Polyploidy: cell division gets messed up resulting in an organism with more than the usual number of chromosomes Ex: strawberry

Only considered a new species when they can ONLY interbreed with each other (other polyploids).

Although harmful in animals, polyploidy is NOT harmful in plants, and can result in a hardier plant.

1. Which type of isolation is typical of two different species and is the result of speciation?

2. If two species are forced to breed in captivity, does that make them the same species?

3. Is polyploidy dangerous?

chapter 15 and 16 (pgs 278-317) mrs. mcnamara biology biology reveals that common genetic sequences...

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