* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download BIO152 Natural Selection 1 Lecture outline
Survey
Document related concepts
The Selfish Gene wikipedia , lookup
Theistic evolution wikipedia , lookup
Saltation (biology) wikipedia , lookup
Sociobiology wikipedia , lookup
Population genetics wikipedia , lookup
Genetics and the Origin of Species wikipedia , lookup
Evolutionary mismatch wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Koinophilia wikipedia , lookup
Sexual selection wikipedia , lookup
Inclusive fitness wikipedia , lookup
Transcript
BIO152 Natural Selection 1 September 20 Lecture 4 Lecture outline • • • • Review-4 attributes of natural selection Example-beak size Freeman 23.3 Artificial selection Freeman 1.2 Alternative hypothesis-inheritance of acquired traits (Lamarck) Box 23.2 1 Natural selection: 4 attributes 1. Only some offspring live long enough to reproduce; some individuals survive and produce more offspring 2. Individuals in a population vary in traits 3. Some variation is passed on to offspring: heritable variation 4. Survival is not random -some heritable traits offer an advantage to survive & reproduce. Table 1 Population growth in Ideal Conditions Initial population Final population 2 elephants 750 years 1.9 x106 2 house flies 5 months 1.9 x1020 1 E. coli 48 hours Cover earth to depth of 2m 2 Table 2 Odds of survival in natural conditions Initial population Final population 100 elephants 750 years later: 130 1000 house flies 5 months: 890 1x106 E. coli 48 hrs: 1.5x106 What factors affect survival? 3 Natural Selection in action Chapter 23 pp 506-508 Also The Beak of the Finch, John Weiner Peter & Rosemary Grant Galapagos Islands: Daphne Major Studied the survival of the medium ground finches during a severe drought in 1977 Where in the world… • Series of slides showing maps to orient you to where the Galapagos Islands are and the ocean currents affecting rain fall and nutrients 4 Currents are like rivers in the ocean. This map shows the complexity of currents surrounding the Galapagos. This situation has profound influences on the Galapagos climate and hence its animals, especially due to the El Niño effect. During El Niño, the cold Humboldt Current from the south slackens off and the islands are bathed in the warm waters of the Panama Current (arrow labeled "Niño Flow"). Water and air temperatures rise and rainfall increases dramatically. Land animals thrive. On the other hand, nutrients the Humboldt normally brings to the islands, fall in concentration so aquatic life, and seabirds that depend on it, suffers. Currents were and still are important in transporting land and sea animals to the Galapagos (see animal origins). (http://www.junglephotos.com/galapagos/gmaps/scimaps/currents.shtml Map modified from Michael H. Jackson, Galapagos: A Natural History Guide) The Grants found that the offspring of the birds that survived the 1977 drought tended to be larger, with bigger beaks. Hypothesis: the adaptation to a changed environment led to a larger-beaked finch population in the following generation. [Figure 23.12] 5 Did natural selection take place? • Variable beak size—yes • Heritable- (yes, birds with larger beaks had offspring with larger beaks) • Differential reproductive success-yes, huge die back, only birds with larger beaks survived Unusually rainy weather in 1984-85 ► More small, soft seeds & fewer of the large, tough ones. The birds best adapted to eat those seeds because of their smaller beaks were the ones that survived and produced the most offspring. Evolution had cycled back the other direction. It is possible to see evolution happen! [Figure 23.13] 6 Artificial selection • [examples- on several slides] Wild mustard Corn Dogs Tulips Natural selection How does natural selection differ from artificial selection? 7 Artificial versus Natural selection • Artificial selection selects for a trait WE deem desirable, not necessarily ones to increase the ability of the organism to survive and reproduce. Artificial selection exaggerates the change in allele frequency in a population for a specific trait & any other linked traits. (Consider the affect of artificial insemination on allele frequency) (Think about this point after we discuss the Hardy Weinberg principle later in the course) Alternative hypothesis to natural selection Jean-Batiste do Lamarck early 1800s Species are not static, but have changed over time Species not independently created entities but are related by common ancestry Earth is incredibly old [He recognized the PATTERN part of evolution] 8 Lamarck’s Process Inheritance of acquired traits 1. Simple forms of life continually created by spontaneous generation. 2. Simple forms evolved into progressively ‘higher’ (larger & more complex) forms 3. Individuals change as they develop to meet the challenges from their environment. • Lamarck did not support the idea of extinction: for him, species that disappeared did so because they evolved into different species. 9 Lamarck’s First Law: use or disuse Organisms are not passively altered by their environment: • Instead, a change in the environment causes changes in the needs of organisms living in that environment, which in turn causes changes in their behavior. • Altered behavior leads to greater or lesser use of a given structure or organ; use would cause the structure to increase in size over several generations, whereas disuse would cause it to shrink or even disappear. Lamarck’s Second Law: Acquired traits are heritable • Use/disuse changes were heritable. • The result of these laws → continuous, gradual change of all organisms, as they became adapted to their environments The physiological needs of organisms, created by their interactions with the environment, drive Lamarckian evolution. 10 While the mechanism of Lamarckian evolution is quite different from that proposed by Darwin, the predicted result is the same: adaptive change in lineages, ultimately driven by environmental change, over long periods of time Lamarckian inheritance, (inheritance affected by use or disuse), is in conflict with the findings of genetics and has now been largely abandoned -- but until the rediscovery of Mendel's laws at the beginning of the twentieth century, no one understood the mechanisms of heredity, and Lamarckian inheritance was a perfectly reasonable hypothesis 11