(Did you read about Lamark?) Do Now: 5/11 Objectives: Define homology and distinguish homologous structures from analogous ones, Use the principle of parsimony to construct a cladogram of maximum likelihood for vertebrate animals. Task: (Did you read about Lamark?) What is the primary difference between Lamark’s theory of evolution and Darwin’s?

Natural Selection in Action This field of corn has lots of weeds in it. Weeds take nutrients from the soil the corn plant needs.

RoundUp Ready Corn RoundUp is a chemical that kills plants. 90% of the corn grown in the US is genetically modified to have resistance to RoundUp. Since the corn is resistant, farmers can spray roundup and kill everything but the corn

It worked for a while…

But there was VARIATION in the weeds A tiny % of the weeds were naturally resistant to the RoundUp and survived… Resistant Weed

Now, that weed had offspring… and they had offspring… etc. etc. Since resistant weeds are the only ones that survive and reproduce, they are now far more common in corn fields. Resistant Weed Resistant Weed Resistant Weed Resistant Weed Resistant Weed

That’s Evolution! An abiotic factor in the environment (RoundUp) has selected a trait in the population of weeds – RoundUp resistance. The weeds have adapted to their environment. Adaptation: 1. the process by which a population becomes better suited in its habitat. 2. A feature that is important to an organism’s survival

Adaptations What adaptations do these organisms have that help them survive? Humans Bears Fish Ducks

Homology = Similarity Homologous structures are alike in basic structure and origin (like flippers and wings) Genetic homology or DNA homology measures how similar DNA sequences are.

DNA Homology

Homology = Relatedness Organisms which share homologous structures or DNA are related to each other. The more homology there is between two organisms, the more closely related they are.

Organisms are Classified by their Similarities and Differences Phylogeny is how groups of organisms are related to each other A cladogram or phylogenetic tree is a diagram that shows these relationships

Cladogram

Making a Cladogram We will be making a cladogram that shows how 7 different organisms are related to one another based on their characteristics

The animals

The Characteristics Paired Appendages Canine Teeth Mammary Glands

Amnion Paired Legs Vertebral Column

Foramen Magnum