BIO152 Pattern & Process

Transcription

1 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/

2 self test quiz on reading assignment Write your answers in your notebook. 9/12/ 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/

3 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/ 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/

4 Explain the implication of the cell theory to Single-celled organisms Multi-celled organisms 9/12/ Important conclusion! All cells in unicellular and multicellular organisms are connected by common ancestry. 9/12/

5 Evolution 9/12/ 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/

6 Evolution = Descent with modification Not simply change over time Trees lose their leaves (not evolution) 9/12/ 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/

7 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/ Process of evolution Natural selection proposed by Darwin & Wallace explained how evolution works 9/12/

8 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/ 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/

9 Natural selection evolution Selection (survival) of individuals with certain traits leads to a change in the characteristics of the population = EVOLUTION 9/12/ 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/

10 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/ 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/

11 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/ Misconception Misconception: Natural selection gives organisms what they need. 9/12/

12 If you don t have the trait, you don t get it! Natural selection acts on genetic variation. 9/12/ 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/

13 Thought question about natural selection Why must traits be inherited by offspring for natural selection to occur? 9/12/ 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/

14 Readings for Monday 1. review Chapter 1 Section Chapter 23 a. Intro pp b. Box 23.2 p 503 c. Section 23.2, web/cd tutorial 23.1 d. Section /12/ 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/

15 PRA101 PRA102 PRA201 PRA202 PRA301 PRA302 PRA401 PRA402 PRA501 Monday Tuesday Wednesday Thursday Friday 9/12/ 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/

16 Lab issues Make your own Lab changes Sept 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 SE daily 9/12/ 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 9/12/

17 Tutorial Friday Read Freeman 1.4 Doing Biology Read Pechenik chap 3 (note taking) & pp Tables & graphs 9/12/