SUMBERDAYA GENETIK DALAM EKOSISTEM

I. PERUBAHAN GENETIK DI ALAM DAN PRODUKSI DIVERSITAS GENETIK Change of environmental conditions Adaptation Natural selection Variation Genetic change Genetic Diversity organism

1. Adaptation Adaptation is : any aspect of an organism or its parts that is of value in allowing the organism to withstand conditions of the environment

Why the organisms have to adapt? 1.Enable an organism to better use resources 2.Provide protection from environmental stresses and pressures 3.Modify local environments to the benefit of the organism 4.Facilitate reproduction

TO SURVIVE ADAPTATION?

Review: overpopulation, unequal survival, unequal reproduction, microevolution Only factor that generally adapts a population to its environment The other three factors may effect populations in positive, negative, or neutral ways 2. Natural selection

Fig 1. The illustration of natural selection

Examples: – Herbivores higher for white flowered plants than red flowered – red-flowered alleles (R) increase – Pollinators attracted by white flowers rather than red flowers – white flower alleles (r) increase. Natural selection accumulates and maintains favorable genotypes

1. Directional 2. Stabilizing 3. Diversifying 4. Sexual Types of natural selection

1. Directional Phenotype moves toward one end of the range Ex. Beak size in Galapago ground finch – During dry years big beaks advantageous and increase in frequency. Fig Type of natural selection

2. Stabilizing selection Fig Frequency of individuals showing a range of phenotypes

Selects for two ends of a range Can result in balanced polymorphism Ex. Beak type in black- bellied seedcrackers – Two types of seeds – hard and soft – Intermediate billed birds inefficient at feeding on either type Fig Diversifying

4. Sexual selection

3. Variation The natural variability Genotype level Phenotype level

Cause of Variation a.Mutation is a permanent change in the DNA sequence that makes up a gene. Mutations range in size from a single DNA building block (DNA base) to a large segment of a chromosome

electromagnetic radiation ( x-rays and gamma rays) cause breaks in phosphodiester bonds and result chromosome mutations like inversions, translocation, duplications and deficiencies

Mutation in a microRNA converts petals to stamens. The mutants of petunia and snapdragon show marked similarity. The studies revealed that, due to a common gene defect, the 'plan' underlying the control of floral organ identity is impaired - resulting in 'the wrong organ at the wrong place'. Image: MPI for Plant Breeding Research

Fig 2. The Hardy-Weinberg equilibrium of allele frequencies in non-evolving populations This equilibrium will hold true no matter what the frequencies of the alleles in the parent population. Try it with p =.24 and q =.76, for example, in a population of 1000 peas. b.Sexual reproduction

Combination of heritable and non- heritable traits Phenotype is the cumulative product of: – Inherited genotype – Environmental influences Only the genetic component can be selected Types of variation a. Phenotypic Variation Fig Same genes, different seasons

b. Genotypic variation Expressed in these ways: – Quantitative (continuous – multilocus?) ex. plant height – Discrete (single locus?) ex. flower color Measured by: – Gene diversity - % heterozygosity Human – 14% – DNA base diversity Human – 0.1 %

c. Geographic variation Between or within populations Natural selection working in response to differences in environment Genetic drift Cline = graded geographic change Fig Geographical distribution of variation in Yarrow plants

Ddi II. SELEKSI DAN DOMESTIKASI Agricultural species (live, grow &reproduce) Human: construct and manipulate the environment Determine and select for traits Cultivate & propagate Directed selection DOMESTICATION

Methods of Directed Selection 1.Mass Selection 2.Pure Line Selection 3.Production of Synthetic varieties 4.Hybridization 5.Induced Polyploidy 6.Biotechnology