Section 17.2 Ideas the Influenced Darwin · •Mountains can be worn down by rain, wind, heat, and cold ... Artificial Selection •In artificial selection, nature provides the inherited

Section 17.2 Ideas that Influenced Darwin

Standards

• LS 4.1 Evaluate scientific data collected from analysis of molecular sequences, fossil records, biogeography, and embryology. Identify chronological patterns of change and communicate that biological evolution is supported by multiple lines of empirical evidence that identifies similarities inherited from a common ancestor (homologies).

Key Questions

1. What did Hutton and Lyell conclude about Earth’s history?

2. How did Lamarck propose that species evolve?

3. How did Malthus explain population growth?

4. How is inherited variation used in artificial selection?

Vocabulary

• Artificial selection

An Ancient, Changing Earth

• Many Europeans during Darwin’s time believed Earth was only a few thousand years old and had not changed much.

• Geologists James Hutton and Charles Lyell concluded that Earth is extremely old and that the processes that changed Earth in the past are the same processes that operate in the present.

Hutton and Geological Change

• Recognized the connections between geological processes and features like mountains and valleys

• Proposed that forces between Earth’s surface can push rock layers upward

• Over long periods, those forces can build mountain ranges

• Mountains can be worn down by rain, wind, heat, and cold

• Most of these processes operate very slowly

• Our planet must be much older than a thousand years

• Deep time- our planet’s history stretches back over a period of time so long its difficult to imagine

Lyell’s Principles of Geology

• Argued that laws of nature are constant over time

• Uniformitarianism- the geological processes we see in action today are the same processes that shaped Earth millions of years ago

• Volcanoes release lava and gases

• Rivers slowly dig channels and carve canyons

• Also argued Earth was much older than thousands of years

Lyell’s Principles of Geology

• Darwin read Lyell’s books during his voyage

• During his voyage, he was able to experience: • A volcano erupt in Chile

• An earthquake that lifted a stretch of rocky shoreline more than three meters

• Fossilized marine animals in mountains

• If Earth can change over time, could life change too?”

-Charles Darwin

Lamarck’s Evolutionary Hypotheses

• Darwin was not the first to suggest that species could evolve.

• Lamarck suggested that individual organisms could change during their lifetime by selectively using or not using various parts of their bodies. He also suggested that individuals could pass these acquired traits to their offspring, enabling species to change over time.

Lamarck’s Ideas

• Proposed that all organisms have an inborn urge to become more complex and perfect.

• As a result, organisms change and acquire features that help them live more successfully in their environments.

• Acquired characteristics- traits altered by an individual organism during its life

• Inheritance of acquired characteristics- if an organism acquired a trait during its lifetime, it could pass that trait on to its offspring

Lamarck’s Ideas

• Flamingos could have acquired long legs because they began to wade into deeper water looking for food.

• As the bird stretched its legs to stay above the water’s surface, its legs would grow a little longer.

Evaluating Lamarck’s Hypotheses

• Lamarck’s hypotheses are completely unsupported.

• Organisms do not have an inborn drive to become perfect.

• Evolution does not mean that a species becomes “better” over time.

• Evolution does not progress in a predetermined direction.

• Traits acquired by individuals during their lifetime are not inherited by their offspring.

• Still, Lamarck was one of the first naturalists to argue that species are not fixed.

• Although his hypotheses were wrong, his ideas paved the way for later biologists.

Population Growth

• In 1798, Thomas Malthus noted that people were being born faster than people were dying.

• Malthus reasoned that if the human population grew unchecked, there wouldn’t be enough living space and food for everyone.

• Malthus suggested that war, famine, and disease work against population growth.

Population Growth

• Darwin realized that Malthus’ observations applied to other organisms as well.

• Many organisms can produce lots more offspring than humans.

• For example, a maple tree produces thousands of seeds.

• Maple trees should eventually overrun the Earth.

• Obviously, this isn’t happening… many die and only a few survive and reproduce.

• Darwin was convinced that species evolved… but he needed a mechanism (a scientific explanation based on natural process)

Artificial Selection

• In artificial selection, nature provides the inherited variations, and humans select those variants they find useful.

• Farmers use this variation to their advantage (selective breeding).

• Darwin made a breakthrough by recognizing that inherited variation provides raw materials for a natural mechanism that could drive evolution.

Section 17.2 Key Questions Exit Ticket

1. What did Hutton and Lyell conclude about Earth’s history?

2. What role did Lamarck think acquired characteristics played in evolution?

3. According to Malthus, what factors limit human population growth?

4. What is involved in the process of artificial selection?

The End