Lamarck's Theory of Evolution and Darwin's Evolutionary Concepts

Lamarck's Theory of Evolution

• The theory proposes a "Tendency toward Perfection", where species develop towards perfection over time, e.g. the giraffe's neck.
• Use and Disuse concept: as birds use their forearms, they develop stronger arms.
• Inheritance of Acquired Traits: species pass on characteristics acquired through use or disuse to their offspring.

Population Growth and Malthus

• Thomas Malthus, a 19th-century English economist, proposed that population growth is limited by insufficient living space and food resources.
• If population grows rapidly, and more babies are born than die, it leads to resource scarcity.

Publication of Origin of Species

• Russell Wallace wrote an essay summarizing evolutionary changes from his field work in Malaysia, prompting Darwin to publish his findings.
• Darwin applied Malthus' theory to animals in his book "On the Origin of Species".

Natural Selection and Artificial Selection

• Natural variation: individuals of a species exhibit differences.
• Artificial selection: humans select and breed organisms with desired traits, enhancing those variations.
• Natural selection results from the struggle for existence, where individuals better suited to their environment survive and reproduce, passing on advantageous traits.

Evolution by Natural Selection

• Over time, natural selection leads to changes in inherited characteristics, increasing a species' fitness in its environment.
• Descent with modification: each living organism has descended with changes from other species over time through common ancestors.

Evidence of Evolution

The Fossil Record

• Fossils show changes in species over time, with transitional forms between ancient and modern species.

Geographic Distribution of Living Things

• Similar environments have similar types of organisms, indicating evolutionary adaptation to specific habitats.

Homologous Body Structures

• Structures with different mature forms in different organisms develop from the same embryonic tissue, indicating a common ancestor.

Similarities in Early Development

• Embryos of different species exhibit similar developmental stages, indicating a shared evolutionary history.

Vestigial Organs

• Organs that serve no useful function in an organism, e.g., the appendix, indicate evolutionary remnants from ancestors.

Summary of Darwin's Theory

• Individuals in nature differ from one another.
• Organisms produce more offspring than can survive, and many non-reproducing individuals do not pass on their traits.