THE THEORY OF EVOLUTION. Darwin, the people who contributed to his ideas, and what it all really means.

Transcription

1 THE THEORY OF EVOLUTION Darwin, the people who contributed to his ideas, and what it all really means.

2 DARWIN S JOURNEY Charles Darwin was born in England on February 12, Geologists were suggesting that Earth was ancient and had changed over time, and biologists were suggesting that life on Earth had also changed. The process of change over time is called evolution. Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors.

3 DARWIN S JOURNEY Darwin sailed on the HMS Beagle for five years! Darwin planned to collect specimens of plants and animals on the voyage.

4 HMS BEAGLE OBSERVATIONS Darwin noticed 3 distinct patterns of biodiversity while aboard the Beagle: Species vary globally Species vary locally Species vary over time.

5 SPECIES VARY GLOBALLY Darwin noticed that different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe. Example: Rhea South America Ostrich Africa Emu Australia

6 SPECIES VARY LOCALLY Darwin noticed that different, yet related, animal species often occupied different habitats within a local area. Example:

7 SPECIES VARY OVER TIME Darwin noticed that some fossils of extinct animals were similar to living species. Fossil: the preserved remains or traces of ancient organisms.

8 DARWIN S CONCLUSION Evidence suggested that species are not fixed and that they could change by some natural process.

9 WHILE DARWIN WAS OUT. Geologists, studying the structure and history of Earth, were making new observations about the forces that shape our planet.

10 WHO CONTRIBUTED TO DARWIN S IDEAS? Hutton and 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. Lamarck Suggested that organisms could change during their lifetimes by selectively using or not using various parts of their bodies. He also suggested that individuals could pass these acquired traits on to their offspring, enabling species to change over time.

11 WAS LAMARCK CORRECT? Lamarck proposed the hypothesis that organisms could change during their lifetimes by selectively using or not using various parts of their bodies. Organisms could change the size or shape of their organs by using their bodies in new ways. Example: If a bird stopped using its wings to fly, its wings would become smaller. Acquired characteristics: Traits altered by an individual organism during its life.

12 WAS LAMARCK CORRECT? Lamarck believed that over time, organisms could pass on their acquired characteristics. This is known as inheritance of acquired characteristics. Today, we know that Lamarck s hypotheses were incorrect in several ways. Organisms don t have an inborn drive to become more perfect. Evolution does not mean that over time a species becomes better somehow, and evolution does not progress in a predetermined direction. Traits acquired by individuals during their lifetime cannot be passed on to offspring.

13 MALTHUS AND POPULATIONS If the human population grew unchecked, there wouldn t be enough living space and food for everyone. Humans were being born faster than people were dying, causing overcrowding.

14 ARTIFICIAL SELECTION Nature provides the variations, and humans select those they find useful. Example: Farmers would select for breeding only trees that produced the largest fruit or cows that produced the most milk.

15 DARWIN PRESENTS HIS CASE In 1859, Darwin published his book On the Origin of Species. Darwin proposed that evolution occurred by natural selection.

16 NATURAL SELECTION Natural selection occurs in any situation in which: 1. More individuals are born than can survive (the struggle for existence) 2. There is natural heritable variation (variation and adaptation) 3. There is variable fitness among individuals (survival of the fittest)

17 THE STRUGGLE FOR EXISTENCE The struggle for existence: more individuals are produced than can survive, members of a population must compete to obtain food, living space, and other limited necessities of life. Sea Turtles

18 VARIATION AND ADAPTATION Individuals have natural variations among their heritable traits, and some of those variants are better suited to life in their environment than others. Adaptation: Any heritable characteristic that increases an organism s ability to survive and reproduce in its environment Adaptations

19 ADAPTATIONS Camouflage: an organisms ability to blend into its background and avoid predation. Mimicry: which an organism copies, or mimics, a more dangerous organism.

20 THE CUTTLEFISH Cuttlefish Video

21 SURVIVAL OF THE FITTEST Fitness: how well an organism can survive and reproduce in its environment. High fitness: Individuals with adaptations that are well-suited to their environment can survive and reproduce Low fitness: Individuals with characteristics that are not well-suited to their environment either die without reproducing or leave few offspring

22 NATURAL SELECTION Natural selection: the process by which organisms with variations most suited to their local environment survive and leave more offspring. Well-adapted individuals survive and reproduce.

23 NATURAL SELECTION EXAMPLE

24 NATURAL SELECTION EXAMPLE

25 COMMON DESCENT Common descent: all species, living and extinct, are descended from ancient common ancestors. Descent with modification: living species are descended, with modification, from common ancestors.

26 DARWIN S TREE OF LIFE Natural Selection