SUMBERDAYA GENETIK DALAM EKOSISTEM
Feb 16, 2016
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 pressures3. Modify local environments to the benefit of
the organism4. Facilitate reproduction
TO SURVIVEADAPTATION?
• 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. Directional2. Stabilizing3. Diversifying4. 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. 23.13
Type of natural selection
2. Stabilizing selection
Fig. 23.12 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. 23.14
3. 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 variationa. Phenotypic Variation
Fig. 23.7 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. 23.8 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 Selection2. Pure Line Selection3. Production of Synthetic varieties4. Hybridization5. Induced Polyploidy6. Biotechnology