Heredity and Evolution — Telangana (SSC) Class 10 Science Solutions (Free)

Heredity: passing of traits from parents to offspring through genes Variation: differences in traits among individuals of same species - Evolution occurs when variations give survival advantages - Organisms with beneficial traits reproduce more successfully - Over generations, advantageous traits become more common in population

Law of segregation: allele pairs separate during gamete formation, each gamete receives one allele. - Example: pea plant height (T = tall, t = short) - Tt plant produces T and t gametes in 1:1 ratio - F1 offspring from Tt × Tt cross: 3 tall : 1 short (genotype 1 TT : 2 Tt : 1 tt) Alternate alleles segregate to produce variation in offspring

Dominant trait: - Expressed in both homozygous (AA) and heterozygous (Aa) individuals - Masks recessive trait Recessive trait: - Expressed only in homozygous recessive (aa) individuals - Hidden in heterozygous (Aa) individuals - Requires two recessive alleles for expression Example: In peas, tallness is dominant over dwarfism

A Punnett square is a grid diagram used to predict genotypic and phenotypic ratios in offspring. - Parental gametes written on axes - Allele combinations filled in grid boxes - Helps determine probability of traits in offspring - Example: Tt × Tt Punnett square shows 1 TT : 2 Tt : 1 tt ratio Useful for predicting results of crosses and understanding inheritance patterns

Evolution: change in inherited characteristics of populations over generations. - Evidence from fossils: shows progression of life forms over time - Comparative anatomy: homologous structures in different species suggest common ancestor - DNA similarity: genetic code universal, DNA sequences similar among species - Observed changes: antibiotic resistance in bacteria, pepper moth color changes - Geographical distribution: species variation across isolated regions

Natural selection mechanism: - Variation exists among individuals in a population - Some variations better suited to environment (fitness) - Organisms with advantageous traits survive and reproduce more - Favorable traits pass to offspring, increase in frequency - Over generations, population evolves to better fit environment Example: Darwin's finches with different beak sizes in different islands

Genetic variation: differences in DNA and alleles among individuals. - Sources: a) Mutation: random changes in DNA create new alleles b) Sexual reproduction: independent assortment and crossing over create new combinations c) Gene flow: movement of alleles between populations - Variation is essential for evolution and species adaptation - Population with greater variation has better survival chances under changing conditions