The Basics of Evolution Chapter 15

The idea of evolution Came from observations made by Charles Darwin when he visited the Galapagos Islands. Observed that organisms differed slightly from one another in different regions Tortoises, finches Evolution – Change in a species over time… new types from existing types OR a hertitable change in a population between generations

What evolution is The concept that species change over time The theory that explains this process is called natural selection, which includes many variables, such as “fitness”, environment, population numbers, predators, genetics, and more Organisms change and adapt based upon biotic and abiotic factors; this can lead to new species Evidenced in antibiotic resistance, new viruses, bird groups, and many more

What evolution is not: Misconceptions Humans did not evolve from monkeys; however, scientists do think that they shared a long-ago common ancestor Completely random: evolution can be affected by many environmental factors An explanation of how life began; instead, it is an explanation of how organisms change over time

Lamarck’s incorrect idea

Age of Earth Until the 1700’s, scientists believed that species never changed. Then, they saw evidence otherwise: Geology: Rock layers date time much farther back: 4.5 billion years ago, as measured by carbon dating Fossils: Fossils found in rock layers are dated back to early times Fossilized organisms resembled today’s organisms, but with differences

Natural Selection A way to explain how species change over time Ways that natural selection might work: Overproduction – environment prevents survival of all Genetic variation – different trait in a population Struggle to survive – competition in environment Differential reproduction – best adapted will reproduce

Anatomy & Embryology Homologous structures – most recent common ancestor shared the same basic structure Ex: human arm, penguin, alligator, bat Analogous structures – closely related functions without a shared common ancestor Ex: wings of birds, moths, and bats

Homologous structures

EVOLUTION Homologous Vestigial Molecules Structures Structures Forelimbs Pelvis Proteins Birds Whales Chickens Mice Dolphins Vertebrates Frogs Humans Rhesus monkeys Lampreys

Diagramming to show relationships Phylogenetic tree – diagram showing relationships of common ancestors, based upon genetics, anatomy, or other relationship information Adaptive radiation – a new population colonizes a new environment by changing to fill many places in the ecosystem

Cladistics Using phylogeny (shared ancestry) to show how a shared characteristics is found within organisms. A way to show evolutionary relationships around a specific feature (feathers, arm bones, seeds, etc)

Cladogram

Cladogram – Part 2

Cladogram Analysis Today, with the advances in genetics and biochemistry, biologists can look more closely at individuals to discover their pattern of evolution, and group them accordingly - this strategy is called EVOLUTIONARY CLASSIFICATION CLADISTICS is form of analysis that looks at features of organisms that are considered "innovations", or newer features that serve some kind of purpose. (Think about what the word "innovation" means in regular language.) These characteristics appear in later organisms but not earlier ones and are called DERIVED CHARACTERS. PART I - Analyze the Cladogram in the previous slide. In the sample cladogram, each letter on the diagram points to a derived character, or something different (or newer) than what was seen in previous groups. Match the letter to its character. Note: this cladogram was created for simplicity and understanding; it does not represent the established phylogeny for insects and their relatives.

Write the letter to match the evolutionary development 1. ______ Wings 2. ______ 6 Legs 3. ______ Segmented Body 4. ______ Double set of wings 5. ______ Jumping Legs 6. ______ Crushing mouthparts 7. ______ Legs 8. ______ Curly Antennae

How species evolve: gradualism vs. punctuated equilibrium