CHAPTER 15 – DARWIN"There is grandeur in this view of life, [that] from such a

simple beginning, endless forms most beautiful and wonderful have been and are being evolved." Charles

Darwin

The Puzzle of Life’s Diversity Evolution – change over time

Process where modern organisms have descended from ancient organisms.

Scientific theory - a WELL tested explanation for a broad set of observations in nature.

It has always been seen to be true.Has not been proven mathematically

Charles Darwin – “Father of Biology”

Born February 12, 1809 (the same day as Abraham Lincoln).

1831- Darwin leaves on the H.M.S. Beagle for a 5 year voyage around the world.

Suffered severe seasickness.

Voyage of the Beagle

Voyage of the Beagle Darwin made many observations and collected

specimens.

Shipped many specimens home

Took a lot of very detailed notes.

Lead him to his Theory of Evolution by Natural Selection.

Darwin’s ObservationsSaw a lot of diversity

1 day in Brazil he collected 68 beetle species.

Saw many patterns of Diversity

Patterns of Diversity Interested in why plants and animals showed such

differences, but were well suited to their environment.

Impressed that organisms survived and produced offspring

Wondered if this process led to the wide variety of organisms.

Patterns of DiversityPuzzled by where different species lived.

Argentina, Australia and Europe had similar grassland but different animals.

Darwin asked: Why were there no rabbits in Australia and why were there no kangaroos in England?

Living Organisms and Fossils Darwin collected many fossils and compared

them to other organisms.

Some resembled other organisms, but others were completely different.

Darwin asked:

Why had so many of these species disappeared?

How were they related to living species?

The Galapagos IslandsGroup of small islands about 1000 km off the west

coast of Equador (S. America).

Each island has a very different climate.

Small islands are hot, dry and nearly barren (not much life).

Higher islands have a lot of rainfall and have much more diversity of plants & animals.

The Galapagos Islands Darwin was fascinated with the land tortoises

and marine iguanas on Isabella Island.

He went from island to island.

Discovered that the shape of the tortoises shell could be used to identify the island where it lived.

The Galapagos Islands Darwin also saw many types of small brown

birds. Collected specimens to be brought home.

Realized that they all had different shaped beaks suited for the seeds they ate.

These birds are known as Darwin’s Finches

The Journey HomeDarwin began to wonder if the animals living on

different islands in the Galapagos had once belonged to the same species.

These species would have evolved from a single S. American ancestor after becoming isolated on the islands.

JAMES HUTTON Theory of Geological Change – 1795 -

detailed theory about geological forces.

Said Earth was not thousands of years old, but millions.

Charles Lyell – Father of Geology

Said scientists must explain past events using processes that they can observe.

These processes are the same now as in the past. Ex. - Erosion (through water) carves out canyons.

Fossils of marine (ocean) animals were found many feet above sea level.

Idea’s that Shaped Darwin’s Thinking Lyell & Hutton influenced Darwin in 2 ways:

If the Earth could change over time, might life change as well?

Realized it would have taken many years for life to change only if the Earth were extremely old.

SEE Biology & History Timeline – pgs. 374-375

Jean-Baptiste LamarckOne of the 1st scientists to see that living things

change over time.

One of the 1st scientists to develop a theory of Evolution.

Saw that species adapt to their environment.

Jean-Baptiste Lamarck1809 - Theory of Use & Disuse (how organisms

change – “use it or lose it”).

Use or disuse of organs means organisms gained or lost certain traits during their lifetime.

Traits are passed to their offspring, leading to change in a species.

Lamarck’s Theory of EvolutionTheory is incorrect because for 2 reasons:

He did not know that traits were inheritedDid not know that an organism’s behavior has no effect

on its inherited traits.

Lamarck’s Theory (See Fig. 15-7, pg. 376).

Population GrowthThomas Malthus – 1798 noticed more babies

being born that people dying.If human population continues to grow, sooner or later

there would not be enough living space and food.

Population growth is controlled by war, famine (no food) and disease.

Population GrowthDarwin realized that Malthus theory applied to

other organisms.Most of a species’ offspring die before they can

reproduce

Darwin Presents His CaseDarwin’s Book: On the Orgin of Species by Natural

Selection – Published in 1859

1858, Darwin read an essay by Alfred Russel Wallace.

Wallace’s essay had the EXACT same conclusions as Darwin (the two never met).

Wallace

Darwin

Darwin Presents His Case

Darwin’s Book: On the Orgin of Species by Natural Selection – Published in 1859

Proposed a mechanism for evolution that he called “Natural Selection” which has been taking place for millions of years and continues in all organisms.

This notion changed the world of science FOREVER.

Natural Selection & Artifical Selection Natural Variation – Differences among individuals of a

species.Ex. – some cows give more milk

Traits passed on to the next generation.

Darwin studied famers and breeders and noticed they used variation to improve crops or animals.

Termed this Artificial Selection (Selective breeding).

Evolution by Natural SelectionStruggle for Existence – members of each species

compete to get food, living space and other necessities of life.

Predators better at getting their prey will have more food.

Prey better at avoiding predators and do not get caught.Example: camouflauge

Survivial of the FittestKey factor in the “struggle for existence”.

How well suited is an organisms to its environment.

Fitness - the ability of an individual to survive and reproduce in its specific environment.

AdaptationAny structure or behavior which allows an organism to

survive in its environment.

Organisms best adapted will reproduce and pass on those traits (adaptations) that help them survive in their environment.

Examples: Porcupines have sharp quills – structural adaptation

Animals that live and/or hunt in large groups – behavioral adaptation

Evidence of EvolutionDarwin argued that living things have been

evolving on Earth of millions of years.

Evidence is found in:The fossil record;The geographical distribution of living species; Homologous structures; and Similarities in early development.

The Fossil RecordThe Fossil Record:

Detailed record of evolution

Darwin pointed out that species of many different forms had appeared on Earth, lived for a time and then vanished.

The fossils that are found in the layers of rock show evidence of the slow change of organisms over time.

Geographic Distribution of Living SpeciesDarwin’s Finches – on the Galapagos

How did these birds become similar, yet different from one another.

Different from other species of finches, but also similar species in S. America.

Concluded that the Galapagos finches could have descended with adaptations from S. American ancestors.

See. Fig. 15-14., pg. 383

COMPARATIVE ANATOMY

Homologous Structures – Structures which are similar in structure, but different in function.

Examples – human hand & bat wing.

Analagous structures – Structures that are similar in function, but different in structure.

Example: Bat wing & bird wing.

COMPARATIVE ANATOMY Vestigial Structures – Reduced in size and

non functional. Example: legs (snakes) and tails (humans – “tail”

bone) and appendix.

No longer needed and become nonfunctional.