The Theory of Evolution by Natural Selection PDF

Module: Natural Selection and Adaptations Lesson 3: The Theory of Evolution by Natural Selection (Summary) What are variations? Variations: are slight differences in inherited traits among individual members of a species. Examples: 1-Giraffes are the same species with different spot patterns 2-Bee O...

Module: Natural Selection and Adaptations Lesson 3: The Theory of Evolution by Natural Selection (Summary) What are variations? Variations: are slight differences in inherited traits among individual members of a species. Examples: 1-Giraffes are the same species with different spot patterns 2-Bee Orchid How does variation occur? Variation occurs by mutations, that produce traits helps an organism to survive. How do variations affect organisms? Effects of Variations Variations can have positive, negative, or neutral effects. Some mutations are beneficial. They produce traits that help an organism survive. The spots help the giraffes blend in with their environment—the grasslands of Africa So the predators such as lions have a more difficult time seeing Giraffe because of spots. Voyage of the Beagle Darwin worked as a naturalist on the HMS Beagle, a ship of the British navy. The ship sailed around the world from 1831–1836. During the trip, Darwin observed plants and animals in their natural habitats and collected them, as well Here are some key themes and observations from the journey: Biodiversity: Darwin noted the incredible variety of species, particularly in the Galápagos Islands. He observed variations among species on different islands, leading him to consider ideas about adaptation and evolution. 1- Tortoises Darwin saw that the giant tortoises on each island looked different. On one island, tortoises had shells that came close to their necks. They could eat only short plants. On other islands, tortoises had more space between their shells and their necks. They could eat taller plants 2- Mockingbirds and Finches Darwin was also curious about the different mockingbirds and finches he saw. Like the tortoises, different types of mockingbirds and finches lived in different island environments. Later, he was surprised to find that many were different enough to be separate species. Darwin’s Theory Darwin discovered a relationship between each species and the food found on the island where it lived. Tortoises with long necks lived on islands that had tall cacti, Tortoises with short necks lived on islands that had short grasses. Natural selection is the process by which populations of organisms with variations that help them survive in their environments live longer, compete better, and reproduce more than those that do not have the variations What are adaptations? Adaptation : is an inherited trait that helps species survive in its environment Types of adaptations Adaptation type Structural Behavioural Functional Definition Physical features Things an Chemical changes of an organism organism do to in body systems Color,neck,fur,ears survive Examples Giraffe long neck Birds migration A drop in body Cheetah's Hibernation temperature powerful legs during hibernation How do adaptations affect organisms? Environmental Interactions 1- Camouflage : is an adaptation that enables a species to blend in with its environment 2-Mimicry: The resemblance of one species to another species Examples: Caterpillar resemble a snake King snake resemble coral snake Camouflage and mimicry are adaptations that help species avoid being eaten. Many other adaptations help species eat. For example, the pelican has a beak and mouth uniquely adapted to eat fish, its main source of food. Another example is the woodpecker, which has a long, thin, sharp beak. Woodpeckers’ beaks help them search for insects in tree bark.