Unit 7: Evolution & Classification Ch 12 & 13 (Evolution, Adaptation, & Speciation)

Unit 7: Evolution & Classification

Ch 12 & 13 (Evolution, Adaptation, & Speciation)

Evolution

The theory that species have

changed gradually over time.

Ch 13 & 14

Evidence to support the Theory of Evolution

• Indirect Evidence– Fossil Record– Comparative Anatomy– Comparative Embryology– Comparative Biochemistry

• Direct Evidence– Current observations

Ch 12.1

Indirect Evidence: Fossil Record• Evidence of:

– change in organisms over time– age of the Earth

• Once living remains of organisms

– Limited:1. Type of material

preserved (bone, shell, impressions, amber)

2. Incomplete record

3. Easily disrupted

Indirect Evidence: Fossil Record

Formation of Sedimentary Rock Layers & Fossilization

Law of Superposition• Which layer is youngest? oldest?

– Explain your reasoning…

• Lower layers = older

• Upper layers = younger

Law of Superposition

Indirect Evidence:Comparative Anatomy

• Compares structures of different organisms living today1. Homologous structures2. Analogous structures3. Vestigial structures

1. Homologous Structures• similar structure w/

modifications• common ancestor

• divergent evolution • becoming more

different

Indirect Evidence:Comparative Anatomy

• 2. Analogous Structures – similar function but

not structure• do NOT have

common ancestor– convergent evolution

» becoming more similar

Indirect Evidence:Comparative Anatomy

• 3. Vestigial structures– reduced size or function

• Often no apparent use

– evidence that organism has changed

Indirect Evidence:Comparative Anatomy

Indirect Evidence:Comparative Anatomy

• Embryonic development– Pattern

• Early stages very similar

• Later stages more distinction

– Inherited same basic body plan from common ancestor

Indirect Evidence:Comparative Embryology

• Trilobites & Horseshoe crab larvae

Indirect Evidence:Comparative Embryology

Indirect Evidence:Comparative Biochemistry

• Similar organic compounds coded for by similar DNA– Ex. proteins

• hemoglobin

Cytochrome c is a protein used in cellular respiration

• DNA most reliable form of evidence– Human & chimpanzees

• 98% similar

– Humans & other mammals• 80% similar

Indirect Evidence:Comparative Biochemistry

• What is the significance of 2 very different species sharing large amounts of the same DNA?– phylogeny

Indirect Evidence:Comparative Biochemistry

• Each generation of organisms in a population shows some variation – result of:

• mutations• genetic recombination

Indirect Evidence:Genetic Evidence

Direct Evidence: Observation• Rapid evolution

1. Antibiotic resistant bacteria

2. Resistance of insects to pesticides

3. HIV strains

1. Antibiotic resistant bacteria

• MRSA

Direct Evidence: Observation

Direct Evidence: Observation2. Pesticide

resistant insects

Mechanisms for Evolution• HOW evolution happens….

– Jean Baptist Lamarck– Charles Darwin– Alfred Wallace

Mechanisms for Evolution• Lamarck vs. Darwin

– Jean Baptist Lamarck (1744 – 1829)1. “Theory of Acquired

Characteristics”– use vs. disuse

» acquired traits are passed on & leads to changes in species

2. Increasing complexity– Experimentation failed to support

Lamarckism

• Do you see any problems with Lamarck’s ideas?– Thought acquired traits could be

passed on…• What information was he lacking?

– He thought that all life was striving upward in complexity.• What do you think of this concept?

Mechanisms for Evolution

Charles Darwin (1809-1882)

Darwin’s Explanation:Gathering Data

• 1. naturalist on HMS Beagle (1831-6)– Collected fossils & specimens– Observed tremendous biodiversity

Ch 12.2

•2. Studied work of geologist Charles Lyell

–“The present is the key to the past.”

•Darwin organisms that are adapted to their environments must also change to remain adapted

Darwin’s Explanation:Gathering Data

–But, Darwin questioned how this change occurred…»Concluded evolution or “descent with modification”

Darwin’s Explanation:Gathering Data

Darwin’s Explanation:In the Galapagos

• noticed unique organisms (yet similar to other forms of the same animals in other parts of the world)– Persuaded Darwin that these organisms were all related to other

known forms

Darwin’s Explanation:In the Galapagos

Saddleback

• long neck, curved shell, found on Hood Island, desert like

Dome-shaped

• shorter neck, domed shell, lush vegetation, covers the ground, Isabela island

The Galapagos Islands

DesertLarge rainfall

Intermediate Shell

Domed Shell

Saddle backed Shell

Climate variation throughout

• Darwin was convinced evolution occurs…– Still needed to test

ideas before explaining how or why such changes happen

Darwin’s Explanation:In the Galapagos

Darwin’s Explanation: Natural Selection• 2 clues led to Darwin’s explanation of how

evolution occurs– 1st clue: Studied work of Thomas Malthus (1798)

• Human population growing faster than resources– Malthus concludes Don’t worry, it will fix itself!

» How? Why?

– How did this influence Darwin’s thinking?

• Darwin applied Malthus’ ideas to other life forms– Overproduction of offspring

» Why is this necessary?

» How might this influence Darwin’s thinking?

Darwin’s Explanation: Natural Selection

–Realized w/ decreased resources struggle for existence

» Survivors – ~Who are they?

~What influences their survival?

~How did they get these traits?

~Were these traits a response to their environment?

Darwin’s Explanation: Natural Selection

– 2nd clue: noted artificial selection (selective breeding)• Used by farmers &

breeders to produce preferred offspring

Darwin’s Explanation: Natural Selection

• Darwin wondered, “Is there a force in nature that simulates artificial selection???”

Darwin’s Explanation: Natural Selection

• Struggle for existence & artificial selection gave Darwin info he needed to explain how evolution occurs– In any given population of organisms there will

be a large variety of traits.• What causes variety?

Darwin’s Explanation: Natural Selection

• Sources of variation– S – sexual reproduction

– C – crossing over during meiosis

– A – arrangement of chromosomes (alleles) during meiosis

– M – mutations

• Darwin did NOT have knowledge of genetics!!!

Darwin’s Explanation: Natural Selection

• Variations can be adaptations– traits that make an organism better

able to survive in its environment

Darwin’s Explanation: Natural Selection

Pepper Moth “Game” http://www.techapps.net/interactives/pepperMoths.swf

Principles of Natural Selection "Interactive"

Camouflage

• Adaptations are NOT a response to the environment– just happen to be “useful” when environment changes

• Any selection that occurs in a population is natural– “survival of the fittest”

Darwin’s Explanation: Natural Selection

– Natural selection & “survival of the fittest”• Individuals best adapted for their environment

have high levels of fitness– Naturally selected for, survive, & reproduce

» More offspring have favorable adaptation than before (if heritable)

Darwin’s Explanation: Natural Selection

Darwin’s Explanation: Natural Selection

• Ex. Pepper Moths – England– Original color – 99% white (trees w/ light bark)

• Industrial Revolution, 1850s – produced smog– Enviro. changes - 1890s - 99% black (trees w/ dark bark)

Darwin’s Explanation: Natural Selection

Pepper Moth “Game” http://www.techapps.net/interactives/pepperMoths.swfPrinciples of Natural Selection "Interactive"

Adaptive Radiation

Adaptive Radiation: Hawaiian Honeycreepers

On the Origin of Species by Means of Natural Selection (1859)

• Summary of Theory of Natural Selection:

1. Overproduction of offspring

2. Variation within population

3. Struggle to survive competition

4. Successful reproduction – “survival of the fittest” (best adapted)

Darwin envisioned the

tree of life

Phylogenetic Tree

How would Darwin adjust the description given by Lamarck about the length of giraffes necks?

• 1858, Alfred Wallace, arrived at same basic explanation as Darwin

• Darwin usually given credit– but BOTH men

should be credited with idea of natural selection

Darwin’s Explanation:Wallace’s Same Conclusion

Population Genetics• Natural selection

acts on individuals, BUT populations evolve– Individual’s genes

stay the same– Population’s gene

pool may change• evolves as allele

frequencies (%) change due to natural selection

• Which trait was a better adaptation and selected for?

• How were frequencies of different alleles affected?

Population Genetics

The “Big Bang” Theory12.3

History of Earth• Earth ~4.6 bill. yrs old

– Early earth• hostile environment

– volcanoes, lightning, meteorites, UV light

• Alexander Oparin – 1936: proposed

primitive atmosphere contained:

» methane, ammonia, hydrogen, water vapor

» What’s missing?

Origin of Life• Life ~3.5 billion

years old

• Stanley Miller (& Harold Urey)– 1953-simulated

primitive atmosphere• zapped w/ electricity

– After 1 week produced amino acids & other simple organic molecules (in water)

» Precursors to 1st cells

• “Primordial Soup Hypothesis” or “Heterotroph Hypothesis”– Simple compounds Complex compounds

Primitive pre-cells Prokaryotes (1st cells)• Heterotrophs

– could not produce their own food & instead fed on the organic material from the primordial soup (in oceans)

– give this theory its name

The First Organisms: Heterotrophs

• Why were heterotrophs 1st?

• Similar to some present-day bacteria– Obtained

energy from simple chemical reactions

The First Organisms: Heterotrophs

• Prokaryotic autotrophs followed heterotrophs– What did they release

into the atmosphere?• produces oxygen – the

oxygen revolution!– Why is this so

important?» development of

eukaryotes & more complex organisms

Later Organisms: Autotrophs

stromatolites