1. define species.. explain this picture. figure 13.00a

1. Define species.

• Explain this picture.

Figure 13.00a

Figure 13.00b

Figure 13.00c

Figure 13.00d

Evolution

Evolution means change over time

The Earth today is not what it once was

• The earth is thought to be 4.5 billion years old

• Life is thought to have appeared ~3.8 billion years ago

• The early atmosphere had methane, carbon monoxide, and

• Essentially no oxygen

Species that exist today did not exist in ages past

• Species of the past are radically different from what exists on earth today

• Converse is true- things that exist today are not seen in the past

Yet there are connections between species of past and present

• Species of today have physical similarities

• This archaeopteryx fossil shows feathers

People did not know the earth was ancient

• Anglican archbishop James Ussher

• October 23, 4004BC: Earth was created

Aquatic forms were found far from land

Charles Lyell proposed that the earth was much, much older

• Posited the idea that continents have moved over time

• Continents move very slowly

• So earth must be very old

Continents can collide to form mountains

• This raises aquatic sediments from ocean bottoms

Charles Darwin became curious about how species came about

• Flunked out of med school

• Didn’t much like Divinity school, either

• Became a naturalist aboard the HMS Beagle

The Voyage of the Beagle

Darwin’s critical observations were comparisons between island

species and mainland species

Marine Iguana and South American Iguana

Flightless cormorants live only on the Galapagos

A Variety of Finches are found in the Galapagos

Finches each have adaptations for different small island environments

Darwin’s inference: The finches have a common ancestor

Likewise, the marine iguanas must have come from the mainland

Evidence for evolution

• Fossil evidence

• Biogeography

• Comparative anatomy

• Comparative embryology

• Molecular biology

Layers of sediment are heaped upon layers over time

Looking down layers is looking back in time

• The principle of superposition

• The layers of the grand canyon go back over 600 million years

Vestigial Structures suggest terrestrial ancestry in whales

Fossil Evidence shows variant species in different layers

Biogeography

• Marsupials are not better adapted to Australia

• Invasive placental mammals are driving many marsupials to extinction

Comparative anatomy

• Similar structures exist in dissimilar animals, serving dissimilar functions

• Homologous structures suggest a common ancestry

Comparative embryology

Figure 13.12a

Figure 13.12b

Evidence from Molecular Biology

• Similar animals have similar DNA sequences

• Less similarity of species= less similarity of DNA

But what was the mechanism?

• How did a species change over time?

• Lamarch proposed a mechanism:

-By repeated strain, a giraffe acquires a long neck

-The long neck is inherited by the offspring

Darwin’s Mechanism: Natural selection

• Those best suited for their environment are selected for survival

• Genes are inherited by the next generation

• Better-adapted species pass on genes suited for the environment

• Next generation is better suited for environment than previous generation

The parts of Darwin’s theory

• 1. Overproduction

• 2. Variation of individuals

• 3. Differential reproductive success

1. Overproduction

• Living things tend to produce more offspring than are able to survive

2. Individual Variation

• Individuals in a species are different from each other

• Some are better adapted to their environment than others

3. Differential Reproductive Success

• Those that are better adapted to their environment are more likely to survive

• Those that survive will pass their genes to their offspring

• Those that don’t, won’t• Do horns on lizards

influence their survival?

Figure 13.17a

Figure 13.17b

Figure 13.17c

• Define evolution.

• Define natural selection.

• Do individuals evolve? Why or why not?

Many people didn’t like Darwin’s theory

• One consequence of the theory is that all living things have a common ancestor

• Humans are closely linked with other primates

• Darwin is disliked today also

Consequences of Natural Selection

• Some insects can tolerate pesticide

• Survivors pass resistance genes to the next generation

• Do these genes exist before the crops are sprayed?

• What other examples are there of this?

What can be said about these insects?

Figure 13.2a

Figure 13.2b

Figure 13.2c

A Population: All individuals of a species in a given area

Individuals in a population have different genes

Hardy-Weinberg Equilibrium

• Some genes are more common than others

• Gene frequencies will result in populations with known genotype frequencies according to algebra’s quadratic equation:

• p2 +2pq + q2 = 1

• Equilibria can be plugged into a Punnett square

Figure 13.20

Genetic Drift

• Natural selection is not the only mechanism by which things evolve

• When populations are finite, gene frequencies can fluctuate by chance

• Small populations flucuate dramatically, large populations less so

Figure 13.22

Consequences of Genetic Drift

• What is gene extinction?• How can genetic drift

remove diversity from a population?

• How can diversity be introduced into a population?

• Do genes drift more in small populations or large ones?

Figure 13.23

Consequences of a bottleneck

• How can a bottleneck reduce diversity in a population?

The Founder Effect-

Genetic drift in a new population

Cheetahs have high genetic similarity between individuals

Figure 13.25

Figure 13.26

Figure 13.27

Kinds of natural selection

• Directional selection

• Disruptive selection

• Stabilizing selection

• Consequences:

• Speciation

• Change in gene frequency

Figure 13.28_1

Figure 13.28_2

Figure 13.28_3

Sources of natural selection

• Predation• Disease

Unnumbered Figure 13_UN267a

Unnumbered Figure 13_UN267b

How old are these fossils?

Radiocarbon (carbon-14) dating can tell the age of fossils

Carbon-14 has a half-life of 5600 years

• Plants take carbon-14 from CO2

• Animals eat plants• When animals die,

the intake of C-14 stops

• Half of C-14 is gone in 5600 years

• The older a sample, the less C-14 it has

How long is C-14 dating useful?

Plate tectonics

• In the bay area, we know that the earth does not sit still

• Sudden, violent movement of geologic plates causes earthquakes

• Meeting of two plates is a fault line

Extra Photo 14.18x

Consequences of plate tectonics

• Environment in various places has changed dramatically

• Antarctica features fossils of tropical creatures

• Continents move slowly, but a billion years is a long time

The Ring of Fire

Mass Extinctions

• Dinosaurs disappeared suddenly 65 million years ago

• Evidence of a large meteor hitting the earth ~65 million years ago on the Yucatan peninsula in Mexico

• Many other extinctions

Permian extinction, 250 mya

• The “Great dying”• Cause unknown• Very large meteor?• 96% of marine

species extinct• 70% of terrestrial

species extinct