Pick up notes for: Cladograms & Dichotomous Keys

Bell Ringer Questions Define Human Taxonomy, and circles the scientific name. Domain: Kingdom: Phylum: Class: Order: Family: Genus: Species:

Agenda Bell Ringer questions Notes on Cladograms & Dichotomous Keys Practice for both Break Work on Q1 Project

Vocabulary Dichotomous Key Convergent Evolution Derived Characteristics Cladogram Modern Classification Mutation Molecular Clock

Traditional Linnaeus Classification Dichotomous Keys use paired statements (yes/no) to describe only the physical characteristics of an organism. Saying “yes” to a statement will lead to another question, and so on. Kind of like a bracket system in sports. After all questions are answered, it leads you to the organisms identity. OR

Dichotomous Key Practice Work with your table group to identify different species of tree by the shape of their leaves. 10min!

Modern Classification Old-school Linnaeus only considered animals and plants body structures (anatomy) to decide how to classify them. This caused a problem for modern taxonomists as scientific research began to look at how animals bodies actually functioned; not just how they looked. Ex: Linnaeus would have classified a dolphin as a fish, because he saw its body had no fur, it had flippers, and lived in the ocean. However, dolphins are actually mammals!

Convergent Evolution When animals live in the same environment they evolve similar body structures with similar purposes, this is due to Convergent Evolution. Ex: Sharks, Ichthyosaurs, and dolphins all have streamlined bodies with flippers because they all live in the ocean. However, when classifying them by how their bodies actually function, the shark is a fish, the ichthyosaur is a reptile, and the dolphin is a mammal! This causes problems when trying to properly classify them.

Darwin’s theory of evolution showed that animals share traits because they share an evolutionary history (ancestors). Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities. So we need a new way to group them instead of using taxons.

Because scientists are now looking at function rather than body shape to group organisms, scientists had to determine which characteristics/function to consider when grouping. Scientists will look at only recently Derived Characteristics that have proven to be essential for that organisms evolution. These derived characteristics will serve as the separate points between organisms, just as the taxon level serve to separation groups of organisms. Ex: lungs, vertebrae, hair, four legs, wings, etc.

Classification Using Cladograms Derived Characteristics with proved to be evolutionary advantages are used to construct a Cladogram: diagram that shows the evolutionary relationship between organism.

Differences in Classification Structure Modern Classification w/ Evolutionary Consideration Linnaeus Way More like a Dichotomous Key

Think-Pair-Share! Describe Convergent Evolution. How are evolutionary relationships important in classification? What kind of diagram shows evolutionary relationships? What are Derived Characteristics?

Cladogram Practice Answer questions on the worksheet with your table group. 10min!

Similarities in DNA All life has genetic information that is passed on by the genes in their DNA. The genes of many organisms can show similarities. These similarities are used to determine their relation and classification. More similarities = closely related.

When the DNA of two organisms is compared, the amount of similarities can also be used to determine how much time has passed since they’d been evolving apart from a similar ancestor. Molecular Clocks use DNA comparison to establish the length of time two species have been evolving independently. Differences in DNA are due to mutations, so Molecular Clocks count mutations. More mutations = less related.

No mutations 1 single species 2 mutations 2 different species 3 mutations 3 different species

Which animal is closely related to humans?

Think-Pair-Share! How can DNA be used to determine evolutionary relationships? How is this different from Linnaeus’ way?

Break for 2 min!

Work on Q1 Disease Projects! Goal for today: Look up at least 4 other organisms that are similar to yours. Construct a Cladogram or Dichotomous Key to add to your Action Plan.