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Sumberdaya genetik dalam ekosistem. I. PERUBAHAN GENETIK DI ALAM DAN PRODUKSI DIVERSITAS GENETIK. Adaptation. Genetic change. Genetic Diversity. Change of environmental conditions. organism. Natural selection. Variation. 1. Adaptation. Adaptation is :

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i perubahan genetik di alam dan produksi diversitas genetik


Genetic change

Genetic Diversity

Change of environmental conditions


Natural selection


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



2 natural selection
2. Natural selection
  • 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


    • 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
types of natural selection
Types of natural selection

1. Directional

2. Stabilizing

3. Diversifying

4. Sexual

1 directional

Type 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. 23.13

2 stabilizing selection
2. Stabilizing selection

Fig. 23.12 Frequency of individuals showing a range of phenotypes

3 diversifying
3. Diversifying
  • 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. 23.14

3 variation
3. Variation

Genotype level

The natural variability

Phenotype level

cause of variation
Cause of Variation
  • 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


Sexual reproduction

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.

types of variation a phenotypic variation
Types of variationa. Phenotypic Variation
  • Combination of heritable and non-heritable traits
  • Phenotype is the

cumulative product of:

    • Inherited genotype
    • Environmental influences
  • Only the genetic component

can be selected

Fig. 23.7 Same genes, different seasons

b genotypic variation
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
c. Geographic variation
  • Between or within populations
  • Natural selection working in response to differences in environment
  • Genetic drift
  • Cline = graded
  • geographic change

Fig. 23.8 Geographical distribution of

variation in Yarrow plants

ii seleksi dan domestikasi


Directed selection

  • Human:
  • construct and manipulate the environment
  • Determine and select for traits
  • Cultivate & propagate

Agricultural species

(live, grow &reproduce)


methods of directed selection
Methods of Directed Selection
  • Mass Selection
  • Pure Line Selection
  • Production of Synthetic varieties
  • Hybridization
  • Induced Polyploidy
  • Biotechnology