ap biology ch. 19 descent with modification

Ch. 19 terms Evolution Paleontology Catastrophism Gradualism Uniformitarianism Endemic species Natural selection

Artificial selection Population Homologous

structures Vestigial organs Molecular

homologies Biogeography

Essential Questions

Please answer Essential Question #1 in this box now.

Essential Questions My initial answer My best answer

What is biological evolution?

What is natural selection?

What are some observations from nature that can be explained by natural selection?

How do evolution and natural selection lead to biodiversity?

Descent with Modification

Ch. 19

Evolution

Change - over time - in the genetic makeup of a population

Over time, enough changes may accumulate in a population for it to be considered a separate distinct species

A Little History Lesson

Georges Cuvier (1769-1832)pioneered the field

of paleontology – the study of ancient lifeObserved that older

fossils in the strata were more different from today’s species that younger fossils

Proponent of the idea of catastrophism - a local catastrophe like a flood wiped out species, and neighboring species moved in to take their place


James Hutton (1726 - 1797)Advocated gradualism - big changes in the

environment can be the result of lots of little changes over a long period of time

The forces shaping the earth today are still at work Rivers carving valleys, for example


Charles Lyell (1797 - 1875)Advocated uniformitarianism -

the idea that geologic processes have not changed over time – i.e. they are still at work


Jean-Baptiste de Lamark (1744-1829) The only one before

Darwin to propose an idea for HOW species change

2 ideas: Use & disuse - used

parts get stronger, disused parts weaker

Acquired characteristics passed on to offspring stronger traits passed

on

Hutton - 1726-1797 Lamark - 1744-1829 Cuvier - 1769-1832 Lyell - 1797-1875

Darwin (1809 - 1882)Liked to collect birds and

bugsDad sent him to med

school at 16He hated it - He had to

watch surgeries done without anestheticLeft after watching a

horrible surgery done on a small child without anesthesia

http://en.wikipedia.org/wiki/Image:Charles_Darwin_1816.jpg

Enrolled at Cambridge to become a clergyman Graduated 10th in his class

Heard about evolution there Heard lectures by James

Audubon about bird adaptations

It was clear to scientists that living things were related & adapted to their environments

The Beagle

Darwin invited to work aboard the SS Beagle in 1831 (he was 22)

The crew surveyed the unmapped coast of South America

Darwin studied the plants & animals Noticed the fossils in SA more similar to current SA species

than to fossils in Europe Noticed geologic differences

Major earthquake hit Chile and he observed the coast rise several feet

These observations challenged the idea of a young, unchanging Earth

The Galapagos Islands

Geologically youngLots of unusual animals thereMany species found only on 1 island

(endemic - found no where else in the world)

Each species uniquely adapted to the conditions (food sources) of its island

Some of the species Darwin observed

Darwin focused on the organisms adaptations

Saw that environmental conditions and adaptations related

The environment

changes

Living things are well

adapted to their

environments

Quick Think

Describe some of the ideas and experiences that

influenced Charles Darwin

The Origin of Species By the 1840s Darwin’s book ready for

publication, but he didn’t publish In 1858 Alfred Russell Wallace (1823-1913)

sent his manuscript to Darwin for review It contained nearly the same ideas as Darwin’s

Darwin published first and was given credit for the theory of evolution by natural selection

Within 10 years, most biologists accepted the ideas The book was well written and very logical and had

tons of evidenceSuper awesome book about Wallace

The Origin of Species

2 main ideas:All species are descendents of earlier, now extinct

speciesNatural selection is the mechanism for evolution






Essential Questions

Please refine your answer to number 1 and answer Essential Questions 2 here now

Natural Selection

Individuals with favorable traits leave more offspring than those without

Eventually results in evolutionary adaptation - an accumulation of traits that increase the chances of survival – this is Darwin’s idea of descent with modification

Darwin’s Logic

Observation 1 - populations will increase exponentially if all offspring survive and reproduce

Observation 2 - populations tend to remain stable in size

Observation 3 - resources are limited

Conclusion

The struggle for resources and the natural overproduction of offspring means that some offspring do not survive to reproduce, thus not passing on their traits to the next generation

Darwin’s Logic

Observation 4 - there is variation among members of a population

Observation 5 - these variations are often inherited from the parents

Conclusion

Individuals that have inherited favorable traits for their environment are more likely to survive and have offspring

The differential survival and reproduction of members of a population leads to gradual changes in the genetic makeup of a population accumulated over many generations

Artificial Selection also influenced Darwin’s thinkingThe selection & breeding of individuals

that have desired traits Crop plants Livestock Pets

Do not resemble their wild ancestors anymore

The Main Points of Natural Selection1. Natural selection is the differential success

in survival & reproduction of individuals in a population

2. Over time, natural selection increases the adaptations found in a population

3. When the environment changes, natural selection may result in new adaptations that may lead to new species






Essential Questions

Please refine your answer to Essential Questions 2 & try question 3 now

3 important points

1. Individuals are selected, POPULATIONS evolve

2. Natural selection acts only on heritable traits

3. Favorable adaptations in one environment may not be favorable in another - natural selection is always at work

Population – a group of interbreeding individuals who live in a particular place at a particular time

Misconceptions

1. Survival of the fittest = survival of the strongest

2. Evolution is not a “grand plan” that will lead to perfectly adapted species

Darwin’s Theory Explains many ObservationsHelps explain why

different species have related parts with different functions

Homology - similar characters resulting from common ancestry

Homologous structures

Darwin’s Theory Explains many ObservationsEmbryos - all vert. embryos have tail and

throat pouches - they develop into different structures in different species

Darwin’s Theory Explains many ObservationsVestigial Organs - structures of little to

no importance to the organism; the remnants of the organism’s ancestors

Darwin’s Theory Explains many Observations

Genetic similarity among organisms – molecular homologies

Biogeography The geographic distribution of species

Closely related species tend to be found in the same geographic region

Similar niches in different places will be occupied by very different speciesThese species may be

similar looking though

Quick Think

Please refine question 3 and answer Essential Question number 4 here nowEssential Questions My initial answer My best answer





The Importance of the Theory of Evolution

In science, there is no such thing as “just a theory”

The theory of evolution is a good theory because: It explains tons of direct

observations and data The process of natural selection

can be tested It is broad and allows scientists to

make new predictions It is constantly being tested and

refined

Quick Think

Please refine Essential Question number 4 here now






ap biology ch. 19 descent with modification

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