Class 10 Chapter 9 – Heredity and Evolution
Heredity and Evolution
- Variations arising during the process of reproduction can be inherited. These variations may lead to increased survival of the individuals.
- Sexually reproducing individuals have two copies of genes for the same trait. If the copies are not identical, the trait that gets expressed is called the dominant trait and the other is called the recessive trait.
- Traits in one individual may be inherited separately, giving rise to new combinations of traits in the offspring of sexual reproduction.
- Evolutionary relationships are traced in the classification of organisms.
- Tracing common ancestors back in time leads us to the idea that at some point of time, non-living material must have given rise to life.
- Evolution can be worked out by the study of not just living species, but also fossils.
- Complex organs may have evolved because of the survival advantage of even the intermediate stages.
Independent inheritance of two separate traits, shape and colour of seeds
Mendel used a number of contrasting visible characters of garden peas – round/wrinkled seeds, tall/short plants, white/violet flowers and so on. He took pea plants with different characteristics – a tall plant and a short plant, produced progeny from them, and calculated the percentages of tall or short progeny.
- Sex is determined by different factors in various species. In human beings, the sex of the child depends on whether the paternal chromosome is X (for girls) or Y (for boys).
- Variations in the species may confer survival advantages or merely contribute to the genetic drift.
- Changes in the non-reproductive tissues caused by environmental factors are not inheritable
- Speciation may take place when variation is combined with geographical isolation
- The process by which new species develop from the existing species is called as speciation
VARIATION IN POPULATION
EVOLUTION AND CLASSIFICATION
- Organs or features may be adapted to new functions during the course of evolution For example, feathers are thought to have been initially evolved for warmth and later adapted for flight.
- Evolution cannot be said to ‘progress’ from ‘lower’ forms to ‘higher’ forms.
- Rather,evolution seems to have given rise to more complex body designs even while the simpler body designs continue to flourish.
- Study of the evolution of human beings indicates that all of us belong to a single species that evolved in Africa and spread across the world in stages.
- Class 10 Chapter 1 – Chemical Reactions and Equations
- Class 10 chapter 2 – Acids, Bases and Salts
- Class 10 Chapter 3 – Metals and Non Metals
- Class 10 Chapter 4 – Carbon and its Compounds
- Class 10 Chapter 5 – Periodic Classification of Elements
- Class 10 Chapter 6 – Life Processes
- class 10 chapter 7 – Control and Coordination
- Class 10 Chapter 8 – How do Organisms Reproduce?
- Class 10 Chapter 9 – Heredity and Evolution
- Class 10 Chapter 10 – Light – Reflection and Refraction
- Class 10 Chapter 11 – The Human Eye and the Colourful World
- Class 10 Chapter 12 – Electricity
- Class 10 Chapter 13 – Magnetic Effects of Electric Current
- Class 10 Chapter 14 – Sources of Energy
- Class 10 Chapter 15 – Our Environment
- Class 10 Chapter 16 – Management of Natural Resources
- Class 10 Question Bank Chapter 1 – Chemicals Reactions and Equations
- Class 10 Question Bank Chapter 2 – Acids, Bases and Salts
- Class 10 Question Bank Chapter 3 – Metals and non metals
- Class 10 Question Bank Chapter 4 – Carbon and its Compounds
- Class 10 Question Bank Chapter 5 – Periodic Classification of Elements
- Class 10 Question Bank Chapter 6 – Life processes
- Class 10 Question Bank Chapter 7 – Control and Coordination
- Class 10 Question Bank Chapter 8 – How do Organisms Reproduce?
- Class 10 Question Bank Chapter 9 – Heredity and Evolution
- Class 10 Question Bank Chapter 10 – Light – Reflection and Refraction
- Class 10 Question Bank Chapter 11 – The Human Eye and the Colourful World
- Class 10 Question Bank Chapter 12 – Electricity
- Class 10 Question Bank Chapter 13 – Magnetic effects of electric current
- Class 10 Question Bank Chapter 14 – Sources of Energy
- Class 10 Question Bank Chapter 15 – Our environment
- Class 10 Question Bank Chapter 16 – Management of Natural Resources