Unit 8: Will only the strongest organisms survive?! Do Now: 1.Base your answer to question A on the diagram below and on your knowledge of biology. The similarities of the bones labeled A provide evidence that the organisms may have evolved from a common ancestor (2) all species have one kind of bone structure (3) the cells of the bones contain the same type of mutations (4) all structural characteristics are the same in animals

We saw the evidence… but HOW does evolution happen?

Theories Explaining Evolution Lamarck Darwin

Adaptation- a characteristic that helps an organism survive. Organisms seem suited for their jobs and environments Organisms seem suited for their jobs and environments Adaptation- a characteristic that helps an organism survive.

Identify the Adaptations!

Lamarck’s Theory Organisms acquire (develop) adaptations to meet their needs in an environment. Specifically, an organism can change its physical traits by using its body in certain ways. The characteristics that an organism acquires during its life are then passed on to offspring.

Lamarck’s theory Crab exercises his claw to make it grow larger Crab passes on the acquired trait to offspring

Narrate this picture! Giraffe Evolution According to Lamarck

Why was Lamarck Wrong? Acquired traits are not inherited (Only traits in DNA are inherited) 5 ?

X Why was Lamarck Wrong? 2. Organisms do not evolve That giraffe will die! X

Darwins Theory: Natural Selection Organisms born with the best adaptations survive and pass on their traits to offspring. Organisms without these adaptations die and do not reproduce. Overtime, the population changes as more organisms inherit the adaptation.

Darwin’s Theory- Natural Selection Crab is born with A slightly larger claw.

X Crab is born with A slightly larger claw.

X Crab is born with a slightly larger claw. Crab with largest claw survives best and reproduces most.

X X X X X Crab is born with a slightly larger claw. Claw helps crab survive and reproduce X X

X X X X X Crab is born with a slightly larger claw. Claw helps crab survive and reproduce X X Eventually, all crabs have the adaptation -the population evolved.

One day a crab is born with an even larger claw…. Natural selection will occur again and the population will continue to evolve

One day a crab is born with an even larger claw…. …Natural selection will continue and the population evolves further Natural selection will occur again and the population will continue to evolve

Giraffe Evolution According to Darwin ?

Partner Practice Read each of the two theories on your notes, which hypothesize how elephants have evolved to have long trunks. Choose a theory, state whether it demonstrates Lamarck’s theory or natural selection and JUSTIFY your answer with evidence. Theory ________ ______________________________________________

TRUE OR FALSE- Write a T next to statements that are true according to Darwin’s Theory of Natural Selection. Write an F next to statements that are false, or that describe Lamarckian evolution. ____ Evolution occurs when organisms adapt to meet their needs in an environment ____ Whole populations, not individual organisms, evolve over time based on their environment ____ Adaptations are inherited ____ Adaptations are acquired based on use ____ If an organism is not well adapted to its environment, it dies ____ If an organism struggles in an environment it adapts