evolution by means of natural selection (ch.10). 10.1 early ideas about evolution teks 2b, 3f, 7b...

Evolution by Means of Natural Selection (Ch.10)

10.1 Early Ideas About Evolution TEKS 2B, 3F, 7B

Early scientists proposed ideas about evolution. • Evolution is the biological change process by which

descendants come to differ from their ancestors.• A species is a group of organisms that can reproduce

and have fertile offspring. (Linnaeus)


Historical thought

• Greek- Aristotle (3rd c. BC)- Scala Naturae- “great chain of being” or the “ladder of life”– Connects all living things moving toward a goal

• Literal Biblical view- the world was created in 6 days– Earth is 6000 years old– all species were created as they are today


de Buffon

• Everything is related; share a common ancestor instead of arising separately

• Goes against any Christian beliefs.

Influence of Geology

James Hutton- gradualismThings that change the earth take A LONG

TIMECharles Lyell- current earth-shaping

processes are the same as the paststressed that scientists must explain past

events in terms of processes that they can actually observe,

Wrote Principles of Geology, read by Darwin

William SmithEach layer (stratum) of rock had unique fossil

recordsThe older the strata, the more dissimilar the

organisms are to present formsGeorge Cuvier

Documented extinction as a common occurrence

Thomas Malthus

Population size link to poverty and disease

If human population continued to grow unchecked (grows expontentially), it will be limited by space and food supply (grows arithmetically)

Population outgrows resources and competition kicks in

That applies to more than just us! Turtles lay hundreds of eggs,

few survive Trees set out hundreds of

seeds, how many actually mature?

There is some selecting factor that decides which organisms are most fit for survival…

Lamarck’s Hypothesis

Tendency Toward Perfection they are continually changing and acquiring features

that help them live more successfully in their environments

Use and Disuseorganisms could alter the size or shape of particular

organs by using their bodies in new ways Inheritance of acquired characteristics

if during its lifetime an animal somehow altered a body structure, it would pass that change on to its offspring

Why/How did giraffes develop long necks?

Lamarck’s Giraffes

Lamarck’s hypothesis of evolution was the first to recognize that organisms are well suited for their environment – this is a key concept for future work.

Lamarck’s Hypothesis (1809)

Charles Darwinmore-complex forms developed from less-complex

formsSpecies on the Galapagos Islands were similar

to the mainland, but differ in each environmentVariation naturally exists within a natural or

domesticated population and some of that variation is inheritable

Galapagos Finches

Alfred Wallace

Co-discovery of natural selectionPublished with DarwinLesser known because he was poor.

So…

Why is Lamarck wrong?

How did his hypothesis positively influence evolutionary thought?

Paleontology

Def: the study of collecting and studying fossils

William SmithEach layer (stratum) of rock had unique fossil

recordsThe older the strata, the more dissimilar the

organisms are to present forms

Fossils provide a record of evolution. Paleontology is the study of fossils or extinct organisms.

Theories of geologic change set the stage for Darwin’s theory.

• There were three theories of geologic change.– Catastrophism Catastrophes cause extinction and promote new

species

– Gradualism slow changes helped to promote new species who are better adapted to the environment

– Uniformitarianism the process that are shaping the earth today have been going on forever

Darwin observed differences among island species.

Variation is a difference in a physical trait.Galápagos tortoises that live in areas with tall plants have

long necks and legs.Galápagos finches that live in areas with hard-shelled nuts

have strong beaks.

Natural Variation in SpeciesDarwin Believed that natural variation already existed in a species and the environment

chose the best suited variation

Darwin did not show a mechanism for how traits were inherited

Galapagos TortoisesMorphology

matched function in the environment.

An adaptations is a feature that allow an organism to better survive in its environment.

– Species are able to adapt to their environment.

– Adaptations can lead to genetic change in a population.

Definitions and Concepts:

Adaptation – any inherited characteristic that increases an organism’s chance of survival and ability to reproduce.Ex. Monarch butterfly is poisonous to eat

they have special coloration to warn predatorsalso viceroy butterflies copy their coloration to protect themselves

Fitness – the ability of an organism to survive and reproduce.

SECTION 3

Theory of Biological Evolution by means of Natural SelectionStruggle for ExistenceSurvival of the “fittest”, or Natural Selection

Fitness- ability to survive and reproduceAdaptations- can be morphological, behavioral, or

physiologicalAn adaptation may be an advantage in one environment

and a disadvantage in another!Natural Selection

Only acts on heritable traitsDoes not form NEW characteristics (only mutations can

do that!) Is backward looking, not plannedacts on the individual, but the effect is on the

POPULATION

Artificial Selection

Man chooses which traits are more appealing to him, then breeds the organism to produce those traits

Theory of Biological Evolution by means of Natural Selection

Species alive today are descended with modification from ancestral species that lived in the distant past.

This process by which diverse species evolved from a common ancestor unites ALL organisms on Earth into a single tree of life.

The story of the Peppered Moth

How did the industrial revolution change a species of moth?

Peppered Moth Animation

Peppered Moth SimulationDiscussion questions:1. What differences were present in the moths?

What caused those differences? Where they differences in morphology or physiology?

2. Before the industrial revolution, which color of organism had the adaptation that was most fit for the environment?

3. What type of selective pressures acted on the moths?

Definitions and Concepts:

Selective Pressure – any phenomenon which alters the fitness of organisms within a given environment. It is the driving force of natural selection, and it can be divided into two types of pressure: biotic or abiotic. Ex: predation, food supply, temperature.

Some antelopes are swift and instinctively run in a zig-zag pattern. Some lions are fast and powerful.

What is the source of variation in antelopes?What is the selective pressure?What is the adaptation that made it successful in the

environment?

Example of selective pressure:

The wide use of antibiotics has caused many bacteria like Mycobacterium tuberculosis to evolve a resistance to antibiotics. Some of the bacteria in this population contained mutant genes that defended the bacteria from the antibiotic drug. These few bacteria did not die when they were exposed to the antibiotic. These resistant bacteria reproduced more bacteria like themselves that were resistant to the antibiotics. This resistance is evidence of change or evolution of a species.

Read the following information and answer the questions on the next slide.

Activity – Bacteria Resistance

1. What was the ultimate source of variation in the species?

2. What was the selective pressure described?3. What was the adaptation of the organism

that made it successful in the changed environment?

4. How did the Mycobacterium tuberculosis change?

Activity – Bacteria Resistance

Thirteen species of finches live on the Galápagos, the famous island group visited by Charles Darwin in the 1830s. The finches have a variety of bill shapes and sizes, all suited to their varying diets and lifestyles. Some birds have beaks better suited for eating cactus; some have long beaks better suited for eating insects, or short beaks for eating hard seeds.

A variety of finches ended up on moist, rainy islands in which there was a shortage of seeds, but many grub-like insects were living under tree bark. The long-beaked birds could survive on grubs, and would pass their genetic traits to their offspring. The others would die out. Natural selection caused the long beaked ‘woodpecker finch’ to survive.

Darwin did not believe that the environment was producing the variation within the finch populations. He correctly thought that the variation already existed and that nature just selected for the most suitable beak shape and against less useful ones.

Activity – Galapagos Finches

1. What was the ultimate source of variation in the species?

2. What was the selective pressure described?3. What was the adaptation of the organism that

made it successful in the changed environment?

4. How did the finch change?

Activity – Galapagos Finches

Deer Mice Deer mice are widespread across North America, but they

usually have dark coat, so that they can blend into dark soils and stay hidden from owls. However, soil in Nebraska is light-colored sand. Over a period of several thousand years the deer mouse in Nebraska evolved a pale coat that helped it to evade predators. Scientists at Harvard and at the University Of California at Berkeley discovered a single gene called Agouti in light colored mice which is expressed in higher amounts and for longer than the genes that code for dark hair. The gene emerged about 4,000 years ago, which was only a few thousand years after the dark coated mice colonized the new sandy home. Its spread was rapid. Agouti did not occur before the colonization of the sandy environment, and when it did appear selection acted on it to confer an advantage, making it more widespread

Activity – Deer Mice1. What was the ultimate source of variation

in the deer mice?2. What was the selective pressure

described?3. What was the adaptation of the organism

that made it successful in the changed environment?

4. How did the population of deer mice change?

1. The term “survival of the fittest” is closely associated with Charles Darwin’s ideas of change over time. If an organism is “fit”, it most likely will –

A. become extinctB. pass down its genes to an offspringC. migrate to a new ecosystemD. change in order to survive

2. Lizards closely resemble the plants and trees in which they live. This is most likely because

A. the lizard has learned to change colors.

B. the lizard is smaller than the leaves of the trees.

C. ancestors of the lizards with the same traits survived and reproduced.

D. the food eaten by lizards lives in plants.

To break it down…

Organisms produce offspring and those that do not survive do not reproduce therefore they do not pass down their genes

Each organism has different advantages and disadvantages in the struggle for existence.

Individuals best suited the their environment survive and reproduce most successfully

Section 4

Evidence of Evolution

includes

which is composed of which indicates which implies which implies

Evidence of Evolution

Physical remains of organisms

Common ancestral species

Similar genes Similar genes

The fossil recordGeographic

distribution of living species

Homologous body structures

Similaritiesin early

development

Figure 15–14 Geographic Distribution of Living Species

Can indicate common ancestry from fossil forms that occupied a continuous area.

Figure 15–14 Geographic Distribution of Living Species

Can indicate similar structures forming due to similar habitats (and therefore similar selective pressures)

NORTH AMERICA

Muskrat

Capybara SOUTH AMERICA

Beaver

Muskrat

Beaver andMuskrat

Coypu

Capybara

Coypu andCapybara

Discuss with your neighbor…What conclusion can you draw from the information below?

Rhea – Native to South AmericaOstrich – Native to AfricaEmu – Native to Australia

Evidence for evolution in Darwin’s time came from several sources.

Fossils provide evidence of evolution.• Fossils in older layers are more primitive than those in upper layers.

Fossil record

Relative age– deeper things are older

radioactive dating gives an estimated age in years.

species that once existed and are now extinct.

uses the layers of fossils older fossils are found below

more recent ones living organisms resemble

fossils although differences may be evident

Relative Dating

using carbon dating on rocks and fossils to determine a more accurate time frame in which the organism lived.

We know how long it takes for radioactive carbon to decay. By identifying how much is left in a sample, we can give it an age.

Radioactive Dating

The Fossil Record shows

transitional forms: fossils or organisms that show the intermediate states between an ancestral form and that of its descendants.

Have you noticed that organisms can be different within the fossil record?

Gradualism – slight changes within a population over time (subtle)

Punctuated equilibrium – a quick change in a population (dramatic - indicates a major event)

Stasis – the idea that during periods of time, little if any change is observed within a population

EXAMINING FOSSIL ACTIVITY

Fossil formation

For every organism that leaves a fossil, many more die without leaving a trace.

Fossil formation

When a fossil is discovered, rarely is it of a complete organism.

More often paleontologists must reconstruct an extinct species from a few fossil pieces—remains of bone, a shell, or leaves.

When paleontologists study a fossil, they look for anatomical (structural) similarities—and differences—between the fossil and living organisms.

Below is a drawing of the fossils found in a partial excavation completed by a paleontologist.

Which layer is the oldest? Which layer is the youngest?

Oldest = F, Youngest = A

Do the layers support the idea that change has occurred over a long period of time?

Yes, water to desert conditions

What might have happened from layer C to layer B?

erosion

Layer A

Layer B

Layer C

Layer D

Layer E

Layer F

Common Ancestry

Common embryology, homologous structures, and DNA comparisons indicate that all living things are related in differing degrees.

Linking organisms together and classifying them based on relatedness is a hot topic among biologists today.

Embryology

Similarity in early embryonic stages shows relatedness.

While this earlycomparison waslater found to bedoctored, it holdsa little truth

Ernst Haeckel

Embryology

Related organisms share a common early embryology The more closely related, the more related their

embryological stages are. When we explore invertebrates and vertebrates, we will

explore comparative embryology in detail

Homologous structures

Structures that arise from the same area of the embryo, but give rise to different mature forms

Turtle Alligator Bird Mammal

Ancient lobe-finned fish

Homology in mammalian appendages

Human hand

Bat wing

Mole foot

Fly wing

Analogous structures are not evidence of a common ancestor.

– Analogous structures have a similar function.

Analogous Structures

Archeopteryx- “finger wing” extended single digit

Bird wing- “arm wing” all “arm” is part of wing

Bat wing- “hand wing” the wing is made up of several elongated digits

Let’s practice: AnaLet’s practice: Analogous & Homologous structures

Vestigial Structures

Structures that have become reduced in size because they do not have a true contributing function or role in survival

Dewclaws (E) in most mammals serve no purpose and have been reduced in size

Vestigial Organs

Pelvic girdle in whales and snakes

Appendix in humans

Eye spots in cave-dwelling animals

• Vestigial structures are remnants of organs or structures that had a function in an early ancestor.

• Ostrich wings are examples of vestigial structures.

Structural patterns are clues to the history of a species.

Homologous, Analogous or Vestigial?

Dolphins (which are mammals) and fish both have similar body shapes adapted for moving in water.

Analogous


This species of cave-dwelling salamander

has eyebuds, but is

completely blind. Vestigial


Giraffe – 7 neck bones

Human – 7 neck bones

Whale – 7 neck bones

Homologous


The ear muscles, appendix, and tailbone in humans.Vestigial


Indicates that two organisms probably have a common

ancestor.

Homologous

Homologous, Analogous or

Vestigial?

aa

b

Compare the entire wing.

What about the yellow

bones?

Between A & B - Analogous

Within A – Homologous

Section 5

Molecular and genetic evidence support fossil and anatomical evidence.

Two closely-related organisms will have similar DNA sequences.

Pseudogenes are sequences providing evidence of evolution.

– no longer function– carried along with functional DNA– can be clues to a common ancestor

Below is a short section of DNA:

A C A T A T T A G

What do the A, C, T and G represent?

Now compare the DNA to a close ancestor:

A C A T A T T A G

A T A T A T T A C

Living organism:

Ancestor:

•On which nucleotide(s) do the sequences differ?•What is this difference called?

You try it! “It’s molecular time” Directions

1. You have 9 nitrogen base sequences from a section of DNA similar to what you might find in a human. Look for the sequence labeled “living DNA”.

2. Find the closest ancestor to the living DNA and place it below the living DNA

3. Place the rest of the sequences in the correct order, from present (living) to oldest ancestor.

It’s Molecular Time Discuss:

What did you use to make your decision? Were you correct in your order?

What did you use to make your decision? Were you correct in your order

It’s molecular time

Assume that the rate of mutation is one mutation for every 10,000 years. How many years separate the “living DNA” from its oldest ancestor?

We can also compare amino acid sequences by looking at how many differences are there

evolution by means of natural selection (ch.10). 10.1 early ideas about evolution teks 2b, 3f, 7b...

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