Natural Selection EQ: How did Charles Darwin’s observations help him develop his theories of natural selection?

Variations in nature There is often a great variation among individuals in nature. Look around the room, what characteristics vary among the members of this class? Why are these variations important?

Trait selections Look at your candy Why did you select it? What candies were selected first? What traits did the selected candies have? What traits did the candies NOT selected have?

Natural Selection This is what natural selection does with individuals in a population. Each individual has unique traits Some traits help an individual survive so that they may reproduce and ensure the survival of their species.

Natural Selection Natural Selection is the process by which organisms that are better adapted to their environment survive and reproduce more successfully than less well-adapted organisms do The process of natural selection has four parts:

overproduction An organism may produce many eggs or offspring so that some will have the chance to survive and develop into reproducing adults.

Inherited variation Each individual organism has its own combination of traits. Each offspring is similar to, but not identical to its parents. This helps “breed out” less desirable traits

Struggle to survive Some organisms are caught by predators, and others may starve or get a disease. Only some of an organism will survive to adulthood The strong are more likely to survive and pass along their “strong” genes

Successful reproduction The organisms that are best adapted (strongest) to their environment are likely to have many offspring that survive, as they will inherit the parents’ “strong” genes.

Natural selection in action The theory of natural selection explains why a population changes in response to its environment. Through ongoing natural selection, a population will adapt to its environment. Well-adapted individuals will likely survive and reproduce.

Adaptations To survive, organisms must adapt to their environment. They must be able to capture their food (predator) and elude being someone else’s dinner (prey) They must be able to resist disease They must be able to compete for mates

Predator/prey adaptations To survive, predators must be able to catch their prey. Predators will have a wide variety of methods and abilities for doing so. Speed, agility, forward facing eyes, acute hearing, attack instinct, camouflage, sharp claws and teeth, etc (choose two)

Predator/ prey adaptations Prey have their own methods and abilities to keep from being eaten: Prey are able to run fast, stay in groups, camouflage themselves. Some are poisonous, have warning coloration. Choose two

Camouflage One way animals avoid being eaten is by being hard to see, Blending in with the background is called camouflage.

Mimicry Other animals use mimicry to blend in with their environment. The organism, such as a walking stick, will resemble a material in the environment, such as a twig, bark, stone or leaves

Adaptations due to hunting Many animals, such as elephants, are hunted for few desirable traits. In the case of elephants, it’s their tusks. As more tusked elephants are killed for their tusks, less survive to reproduce and pass along the trait of being tusked. This leaves the tuskless elephants behind to reproduce, and pass along their trait of being tuskless. The number of tuskless elephants has risen dramatically because of hunting.

Resistance to disease A population may develop a trait to resist disease and/or specific chemicals. Antibiotics, insecticides Most organisms are killed by the disease/chemical, but the ones that do survive continue to reproduce and pass along their adaptation to their offspring. After several generations, almost all of the organisms will have the adaptation

Competition for mates For organisms that reproduce sexually, competition for mates can select for adaptations. Coloring, calling, hormones, abilities, etc. are all adaptations that organisms have in order to attract mates and perpetuate a species. The desirable traits are then passed along to their offspring

Speciation Sometimes, a population of a species is separated from the rest due to a newly formed canyon, mountain building, island forming, etc

Speciation A new species may form after a group becomes separated from the original population. Over time, the new group adapts to its environment. Eventually, the new population and the original population differ so greatly that they can no longer mate. EX: Brown Bears/Polar Bears The formation of a new species as a result of evolution, or change is called speciation.

Think about the candy selections at the beginning of class… Some people took their second favorite type of candy once their first type had all been eaten. Describe how this relates to a predator/prey relationship in nature. Imagine the candies could "adapt" to their environment. Propose two ways the most desirable candies could possibly adapt to survive being eaten.