BIO152 Pattern & Process Lecture 2 Wednesday September 13 Pattern & Process cell theory & evolution Lecture 2 Cell theory Evolution by natural selection (introduction) Course mechanics & reminders 9/12/2006 2 1
self test quiz on reading assignment Write your answers in your notebook. 9/12/2006 3 1. Which statement(s) is/are not part of the cell theory? a. All living organisms are made of cells. b. All living organisms are multicellular. c. Cells arise from preexisting cells. d. Cells contain DNA. 9/12/2006 4 2
2. The pattern component of the cell theory claims that all organisms consist of cells; the process component states that cells arise from pre-existing cells. A. true B. false 9/12/2006 5 3. Pasteur's experiment with the swan-necked flask rejected the spontaneous generation hypothesis by demonstrating that a. Cells can grow in broth after it has been boiled. b. Cells grow in broth unless the broth is sealed off from the air. c. Cells grow only in broth exposed to a source of preexisting cells. d. Bacteria, but not fungi, can grow in broth. 9/12/2006 6 3
Explain the implication of the cell theory to Single-celled organisms Multi-celled organisms 9/12/2006 7 Important conclusion! All cells in unicellular and multicellular organisms are connected by common ancestry. 9/12/2006 8 4
Evolution 9/12/2006 9 The Theory of Evolution (Darwin & Wallace and others) Patterns exist in the natural world 1. Species are related by common ancestry. 2. Characteristics of species can change from generation to generation. (Chap 1.2 & Table 23.1) 9/12/2006 10 5
Evolution = Descent with modification Not simply change over time Trees lose their leaves (not evolution) 9/12/2006 11 Simple change is not biological evolution Erosion of land or mountains which have risen or fallen is not evolution Related organisms have changed over time = [biological] evolution 9/12/2006 12 6
Pattern of evolution Pattern: species are not independent and unchanging entities but are related to one another and can change through time. Even in the mid-1800s many people accepted the pattern, but didn t understand the process. 9/12/2006 13 Process of evolution Natural selection proposed by Darwin & Wallace explained how evolution works 9/12/2006 14 7
Natural selection 1. More individuals are born than survive and reproduce. 2. Individuals vary in characteristics which are heritable. 3. Certain heritable characteristics help individuals survive and reproduce better than other characteristics. 9/12/2006 15 Natural selection: 4 steps 1. Variation-individuals in a population vary in traits 2. Inheritance-some variation is passed on to offspring 3. Survival-only some offspring live long enough to reproduce; some individuals produce more offspring 4. Survival is not random -some heritable traits offer an advantage 9/12/2006 16 8
Natural selection evolution Selection (survival) of individuals with certain traits leads to a change in the characteristics of the population = EVOLUTION 9/12/2006 17 Adaptation A trait which increases an individual s ability to survive and reproduce. Wheat example in text: in windy environments, wheat plants with shorter stocks have an advantage over taller plants. Short stocks are an adaptation to windy environments. [an adaptation is the outcome of natural selection] 9/12/2006 18 9
Natural selection Occurs when heritable variation in certain traits leads to improved reproductive success = Biological fitness Adaptation is a trait which confers reproductive success 9/12/2006 19 Important implications 1. At what level does natural selection happen? a. Individuals b. Populations 2. At what level does evolution happen? a. Individuals. b. Populations. 9/12/2006 20 10
Misconception Misconception: Natural selection involves organisms trying to adapt. You either have it or you do not! Natural selection leads to adaptation, but the process doesn t involve trying. Natural selection involves genetic variation and selection among variants present in a population. Either an individual has genes that are good enough to survive and reproduce, or it does not but it can t get the right genes by trying. 9/12/2006 21 Misconception Misconception: Natural selection gives organisms what they need. 9/12/2006 22 11
If you don t have the trait, you don t get it! Natural selection acts on genetic variation. 9/12/2006 23 Wheat plants windy environment 1. Variable heights in wheat plants. 2. Shorter plants grow & reproduce more than taller plants. 3. Over several generations there are more short plants in windy environment than tall plants. 9/12/2006 24 12
Thought question about natural selection Why must traits be inherited by offspring for natural selection to occur? 9/12/2006 25 Extension question about natural selection Name a trait for each of the following organisms that might help some individuals survive and reproduce more offspring: rabbit cat maple tree bacteria 9/12/2006 26 13
Readings for Monday 1. review Chapter 1 Section 1.2 2. Chapter 23 a. Intro pp 494-495 b. Box 23.2 p 503 c. Section 23.2, web/cd tutorial 23.1 d. Section 23.3 9/12/2006 27 Course Mechanics: Labs This week for Prelab Labs cycle 1 (PRA0x01) 2:00pm. Labs cycle 2 (PRA0x02) 3:30pm. Lab Rooms-posted on wall outside SE1085/87 each morning for that day 9/12/2006 28 14
PRA101 PRA102 PRA201 PRA202 PRA301 PRA302 PRA401 PRA402 PRA501 Monday Tuesday Wednesday Thursday Friday 9/12/2006 29 Lab 1 and beyond Normally you will attend labs every two weeks: 01 starts week of Sept 18 th lab 1 02 starts week of Sept 25 th lab 1 (Lab 1 linked to Lab section of course web page) 9/12/2006 30 15
Lab issues Make your own Lab changes Sept 14-18 th Starting tomorrow (Thursday Sept 14 th ) ONLY on STORM (do NOT use ROSI) Go to Marks on course web page --sign into STORM Login = your student number Password = Familyname exactly as it appears in ROSI Help with STORM see Marianne SE1081 Help with lab content see Dr. Kaicker SE1087 11-12 daily 9/12/2006 31 Read BIO152 Course info on course webpage Lecture notes, news LAB Manual Print & study each lab Bring your copy to lab! Quiz at the beginning of each lab http://www.utm.utoronto.ca/~w3bio152 9/12/2006 32 16
Tutorial Friday Read Freeman 1.4 Doing Biology Read Pechenik chap 3 (note taking) & pp 168 170 Tables & graphs 9/12/2006 33 17