Topic 4 Cell Theory & Natural Selection

Cell Theory CELL = smallest units in living things 1. All organisms are made up of one or more cells (may be a single cell or made up of many cells)

Cell Theory 2. All cells carry on life activities. (structure and function) CELL = smallest units in living things

Cell Theory 3. New cells arise only from other living cells by the process of cell division CELL = smallest units in living things

Development of Cell Theory Robert Hooke Boxlike structures in cork = “Cells”

Development of Cell Theory Anton van Leeuwenhoek Observed and described living organisms found in pond water.

Development of Cell Theory Robert Brown Noticed small, dense centers in cells (nucleus), but function was not known

Development of Cell Theory Matthias Schleiden All plants were made of cells.

Development of Cell Theory Theodor Schwann All animals were made of cells.

Development of Cell Theory Rudolf Virchow All cells come from preexisting cells.

Cell Types Prokaryotes & Eukaryotes

Evolution : The change in species over time.

Theory of Evolution A. Lamarck’s Theory He felt that if an organ or a body part was used a lot, it would become stronger. If it was not used, it would weaken. He also believed that these changes would pass from generation to generation.

A. Lamarck’s Theory Theory of Evolution For example, Lamarck believed that as a giraffe stretched its neck, it became longer. Then baby giraffes inherited a longer neck from their parents.

A. Lamarck’s Theory Theory of Natural Selection His theories were disproved by experiments and are no longer believed because ONLY CHANGES IN GENES ARE PASSED ON.

Theory of Natural Selection B. Darwin’s Theory Darwin was an English scientist who, during a voyage to South America, carefully examined abundant plant and animal species. These observations convinced him that animals change over time.

Theory of Natural Selection B. Darwin’s Theory In 1838 Darwin came up with his theory of natural selection which is made up of four main parts: 1. More Organisms are Born Than Survive - The environment will eventually run out of such things as food, water and space.

Theory of Natural Selection B. Darwin’s Theory In 1838 Darwin came up with his theory of natural selection which is made up of four main parts: 2. Organisms are not all the same (variation) - some organisms are better suited to survival - example: a lightweight skeleton is a favorable characteristic for a bird and a bird with a heavy skeleton is at a disadvantage

Theory of Natural Selection B. Darwin’s Theory In 1838 Darwin came up with his theory of natural selection which is made up of four main parts: 3. Organisms with best suited characteristics survive and reproduce - those with less helpful characteristics die (survival of the fittest) - the offspring that survive pass these helpful characteristics to the offspring

Theory of Natural Selection B. Darwin’s Theory In 1838 Darwin came up with his theory of natural selection which is made up of four main parts: 4. Competition exists among the individuals of the same population

Examples of Natural Selection The beaks of Darwin’s finches. The finches of the Galapagos islands were adapted to the island in different ways, but are believed to share a common ancestor.

Examples of Natural Selection Peppered moths and industrial pollution: Natural selection favored dark-colored moths in areas of heavy pollution, while light colored moths survived better in less polluted areas.

How Do We Get Variation? 1. Mutations in DNA (some are good, some are not) 2. Sexual Reproduction (get a new combination of genetic information) 3. Immigration and Emigration (organisms moving in and out of a population change genetic characteristics of a group)

Topic 4 Assignment 1. Finish questions on cell theory. 2. Read page 610-613 3. Complete questions #1-4 (pg. 613) 4. Color Darwin’s finches.