LESSON PLAN
Forms : 6 Al- farabi
Number of students : 25 persons
Date : 8 May 2012
Time : 9.00 a.m – 11.00 a.m
Subjects : Biology
Title : Natural selection
Learning outcomes :
At the end of lessons, students are able to :
1) to determine the concept of the natural selection and type of natural selection
2) to understanding about genetic mutation
3) can related with dominates, recessive and pedigree
Teaching and learning aids : video, natural selection simulation, rabbits
Moral values : bravery, grateful, responsible, helpful, loving, caring and respected, also teamwork
Strategic : multiple intelligences
1) logical
2) visual and spaces
Critical Thinking skills : generating ideas, sequencing, visualizing, making analogies, prediciting, relating and making conclusions.
Introducation
Natural selection is the process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations.
Natural selection is the gradual, non-random, process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution.
Variation exists within all populations of organisms. This occurs partly because random mutations cause changes in the genome of an individual organism, and these mutations can be passed to offspring. Throughout the individuals’ lives, their genomes interact with their environments to cause variations in traits. (The environment of a genome includes the molecular biology in the cell, other cells, other individuals, populations, species, as well as the abiotic environment.) Individuals with certain variants of the trait may survive and reproduce more than individuals with other variants. Therefore the population evolves. Factors that affect reproductive success are also important, an issue that Charles Darwin developed in his ideas on sexual selection, for example.
Natural selection acts on the phenotype, or the observable characteristics of an organism, but the genetic (heritable) basis of any phenotype that gives a reproductive advantage will become more common in a population (see allele frequency). Over time, this process can result in populations that specialize for particular ecological niches and may eventually result in the emergence of new species. In other words, natural selection is an important process (though not the only process) by which evolution takes place within a population of organisms. As opposed to artificial selection, in which humans favour specific traits, in natural selection the environment acts as a sieve through which only certain variations can pass.
Natural selection is one of the cornerstones of modern biology. The term was introduced by Darwin in his influential 1859 book On the Origin of Species,[1] in which natural selection was described as analogous to artificial selection, a process by which animals and plants with traits considered desirable by human breeders are systematically favored for reproduction. The concept of natural selection was originally developed in the absence of a valid theory of heredity; at the time of Darwin's writing, nothing was known of modern genetics. The union of traditional Darwinian evolution with subsequent discoveries in classical and molecular genetics is termed the modern evolutionary synthesis. Natural selection remains the primary explanation for adaptive evolution.
General Principles
Natural variation occurs among the individuals of any population of organisms. Many of these differences do not affect survival (such as differences in eye color in humans), but some differences may improve the chances of survival of a particular individual. A rabbit that runs faster than others may be more likely to escape from predators, and algae that are more efficient at extracting energy from sunlight will grow faster. Something that increases an animal's survival will often also include its reproductive rate; however, sometimes there is a trade-off between survival and current reproduction. Ultimately, what matters is total lifetime reproduction of the animal.
Types of natural selection
Natural selection can take many forms. To make talking about this easier, we will consider the distribution of traits across a population in graphical form. In we see the normal bell curve of trait distribution. For example, if we were talking about height as a trait, we would see that without any selection pressure on this trait, the heights of individuals in a population would vary, with most individuals being of an average height and fewer being extremely short or extremely tall. However, when selection pressures act on a trait, this distribution can be altered.
Figure 1.1: The standard distribution of a trait across a population
Stabilizing selection
When selective pressures select against the two extremes of a trait, the population experiences stabilizing selection. For example, plant height might be acted on by stabilizing selection. A plant that is too short may not be able to compete with other plants for sunlight. However, extremely tall plants may be more susceptible to wind damage. Combined, these two selection pressures select to maintain plants of medium height. The number of plants of medium height will increase while the numbers of short and tall plants will decrease.
Figure 1.2: The effect of stabilizing selection on trait distribution
Directional selection
In directional selection, one extreme of the trait distribution experiences selection against it. The result is that the population's trait distribution shifts toward the other extreme. In the case of such selection, the mean of the population graph shifts. Using the familiar example of giraffe necks, there was a selection pressure against short necks, since individuals with short necks could not reach as many leaves on which to feed. As a result, the distribution of neck length shifted to favor individuals with long necks.
Figure1.3: The effect of directional selection on trait distribution
Disruptive Selection
In disruptive selection, selection pressures act against individuals in the middle of the trait distribution. The result is a bimodal, or two-peaked, curve in which the two extremes of the curve create their own smaller curves. For example, imagine a plant of extremely variable height that is pollinated by three different pollinators, one that was attracted to short plants, another that preferred plants of medium height and a third that visited only the tallest plants. If the pollinator that preferred plants of medium height disappeared from an area, medium height plants would be selected against and the population would tend toward both short and tall, but not medium height plants. Such a population, in which multiple distinct forms or morphs exist is said to be polymorphic.
Figure1.4: The effect of disruptive selection on trait distribution
Teaching and learning Implementation
| PHASE | CONTENTS | TEACHING AND LEARNING ACTIVITIES | NOTES |
| Inducation Set ( 10 Minutes) | -Relating a video about natural selection and types of natural selection with learning outcomes | 1. teacher show a video about moth that have variety shape and colour. 2. teacher ask question to the students about their understanding on that video shown. 3. teacher related that video with examples of natural selection. 4. teacher relate the video with learning outcomes. . | 1. students get general idea from the video about natural selection 2.students see and listen explanation from teacher Critical thinking skills: -generating ideas - focus Values : -brave T & L Aids : video |
| Step 1 (20 Minutes) | To introduct the meaning of natural selection and types of natural selection and also the factor of natural selection | 1. guru show the power points slide notes about the natural selection 2. teacher gives all the student mind map for the natural selection 3. teacher ready with interesting power point that easy the students to understand that notes. 4. Also have many picture help student to understand. | 1. students write the notes that teachers show. 2.students give their all attention about teaching of teachers Critical thinking skills: -generating ideas - focus Values : - loving -caring T & L Aids : laptop and LCD |
| Step 2 (20 Minutes) | - concept of natural selection | 1. teachers divided into five groups with five people per group 2. teacher show the demo to use natural selection simulation. 3. teacher gives students 10 minutes to explore the simulation using to computer 4. teacher ask students to share what they found. 5.teacher give present (such as chocolates) to student, that can share what they found in the simulation. 6. teacher asked each group to present an what they get from using simulation | 1. students move from the original sit to find the group. 2. students explore using the simulation 3. students exciting to see the simulation. 4. every student want to share anfwhat they found. Critical thinking skills: -generating ideas - exciting Values : -brave - confident T & L Aids : computer |
| Step 3 (20 Minutes) | Natural selection related with genetic mutation, dominates, recessive. | 1. teacher explain more detail to student about contain inside natural selection simulation 2. teacher bring 5 rabbits, which have variety size, shape and colour . 3. teacher gives instruction to press “ add mutation” to want student to see what happen. 4. teacher related topic mutation, natural selection, dominates and recessive with the rabbits in the class and the rabbit in the simulation. 5. teacher ask student to list the physics characteristics of rabbits | 1. students see the real rabbits very clear. 2.students list the physics characteristics the rabbits to get more understanding about mutation. 3. students write the explanations from teacher. 4. student ask teacher what they do not understanding about this topic. Critical thinking skills: -generating ideas - cooperation -communication Values : -brave - intellectual curiosity T & L Aids : real rabbits, slides. |
| Step 4 (20 Minutes) | Pedigree | 1.Teacher ask student to draw the pedigree rabbit with click any rabbit in the simulation. 2. teacher explain about pedigree with student with variety examples. 3. then, teacher ask all of students to draw their own pedigree same like pedigree in the rabbit starting from their grandparents until now. 4. teacher want volunteer to tell all their friends about their pedigree family. | 1. students do what teacher ask and draw the pedigree of rabbit. 2. some of the students like to share their pedigree family. Critical thinking skills: -generating ideas - focus Values : -brave - respectful T & L Aids : A4 paper, pen |
| Step 5 (20 Minutes) | To understanding their understanding about the lecture given | 1. teacher gives assignment group with different questions to each group related with natural selection and using natural selection simulation. 2. teacher provides tool to find information such as new papers , magazines, and books to help student to solve that questions. 3. teacher ask students to each group prepare presentations using majong paper. 4. teacher asked student what they understanding related with topic today. | 1. students answer the questions teacher ask. 2. students find information using material from teacher. 3. student make presentations with variety mind map and extra knowledge. Values: -cooperation -helpful |
| Conclusion ( 10 Minutes) | Get reinforcement exercises and make some summary the topic today | 1. teacher ask student to sit their original places. 2. teacher get some exercises to student and teacher give time to make that exercise and then submit before tomorrow evening. 3. teacher make short conclusion. | 1.Students do that exercise. 2. student get more detail idea about natural selection. Values : - responsible - brave |
