Catalyst 5 minutes to complete, extra credit to finished on Thursday’s Test What do you think the word ‘Evolve’ means? What are dinosaurs closest ancestors?

Announcements Test on Thursday! Review on Wednesday (this will be fun ) Tutoring for test changed to Wednesday afternoon

Origins of Life December 16 th, 2012

Original Idea Once thought that life came from spontaneous generatio, meaning life came from nonliving things. This is abiogenesis.

Disproved Redi’s experiement tested whether maggots (living things) spontaneously generated from meat (dead tissue)

Remi

Pasteur This scientists used beef broth to prove that microorganisms (bacteria)

Remi and Pasteur’s experiments proved biogenesis

So… if life has to come from living things, how did life first start? Atmosphere of earth Earth contained gases Gases reacted with enery from lightening to produce small organic molecules (amino acids)

In the 1950’s Miller and Urey filled a flask with hydrogen, methane, ammonia, and water to represent the early Earth and they used electric lightning to stimulate the mixture. In a few days, organic compounds had formed! This suggested that life can be made from simple compounds on the primitive earth

Miller and Urey

Evolution of Cells The first true cells were heterotrophic prokaryotes They evolved the ability to do photosynthesis to make their own food Photosynthetic prokaryotes were responsible for the release of oxygen into the atmosphere Oxygen was toxic to many organisms who died off Eukaryotic cells probably arose through a symbiotic relationship between two kinds of prokaryotic cells: We believe that mitochondria and chloroplasts used to be prokaryotes (They have their own DNA)! A photosynthetic bacteria (future chloroplast) and an aerobic heterotroph (future mitochondria) found their home inside the cells

Evolution The diversity of life on earth may be understood through the study of evolution. Evolution – the gradual change in the characteristics of a species over time.

Species – a group of organisms whose members look alike and successfully reproduce among themselves.

What is the origin of the concept of evolution? Fossils interested scientists in evolution.

Evidence for Evolution 1. Fossils show changes over time. - Fossils provide a record for earlier life.

2. Anatomical relationships – similarities in the structure of an organism. Evidence that organisms evolve from a common ancestor. Homologous structure are body parts that are similar in structure, in function, or in both structure and function.

Homologous Structures

Analogous structures are body parts that are similar in function, but different in structure. ex. Wings of a bird and a butterfly Vestigial structures any body structure that is reduced in function. May have been of use to an ancestor. ex. flightless birds (ostrich), appendix in humans

3. Embyological Development shows evolution from a common ancestor. ex. The presence of gills and tails in the early stage of all vertebrate embryos. 4. Genetic Comparisons may also show relationship of different species. Can also helps us tell how closely related or how different species are ex. Order of DNA and RNA nucleotides