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