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No Two Organisms Are Identical In All Their Traits
Definition
Variation
Variation refers to differences in traits among individuals within a population, encompassing physical characteristics, behaviors, and genetic sequences.
- Variation can manifest as differences in:
- Morphological traits: e.g., fur color in cats, height in plants.
- Behavioral traits: e.g., bird mating displays, migration patterns.
- Biochemical traits: e.g., enzyme variants, antibiotic resistance in bacteria.
Note
Even closely related organisms, such as siblings, exhibit variation because each inherits a unique combination of alleles during reproduction.
How Genetic and Environmental Factors Cause Variation
Genetic Causes
- Every individual of a species has a unique combination of alleles, except in the case of identical twins or clones.
- Genetic variation is introduced by:
- Mutation: Permanent changes in DNA sequences create new alleles.
- Meiosis: Processes such as crossing over (exchange of DNA between homologous chromosomes) and independent assortment of chromosomes create novel genetic combinations in gametes.
- Fertilization: Random fusion of gametes during sexual reproduction ensures that each zygote is genetically unique.
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- A3.1.1 Variation between organisms as a defining feature of life
- A3.1.2 Species as groups of organisms with shared traits
- A3.1.3 Binomial system for naming organisms
- A3.1.4 Biological species concept
- A3.1.5 Difficulties distinguishing between populations and species