Class 10 Heredity and Evolution Notes
The study of heredity and evolution is one of the most exciting science topics. Both heredity and evolution are processes that involve changes in organisms over time. In humans, heredity involves the transfer of traits from parents to offspring through genes. Evolution, on the other hand, refers to a wide range of processes that lead to changes in the frequency of alleles (or gene variants) within a population of organisms. In this article, you will learn about class 10 heredity and evolution in detail.
What is Heredity?
Heredity is the passing of traits from parents to offspring. In other words, it is the biological phenomenon by which traits are transferred from one generation to the next. It is important to understand that while the traits themselves may be the same, the degree to which they are expressed may differ. There are three main types of traits:
- Phenotypic traits: These traits are what you can see in an organism. For example, skin colour or height are phenotypic traits. Environmental factors can influence phenotypic traits.
- Genotypic traits – These are the underlying genetic traits that determine the kind of phenotypic traits an organism will display. Genotypic traits are the same in all organisms of a species.
- Genetic traits are passed from one generation to the next. Heredity is the process by which genes are transferred from one generation to the next. It is a mechanism by which genes are passed from parent organisms to their offspring.
Types of Inheritance
Mendelian Inheritance: Mendelian inheritance is a type of inheritance which represents that traits are passed from parent to offspring. It is named after Gregor Mendel, the father of modern genetics. In this type of inheritance, one gene from each parent is randomly paired with a gene from the other parent to create the traits of their offspring.
Linear Inheritance: Linear inheritance represents that phenotypic traits of organisms remain the same throughout their lifetimes. In other words, there is no variation in the traits throughout their lifetimes. However, when organisms reproduce, their offspring may or may not inherit those traits.
Epigenetic Inheritance: Epigenetic inheritance represents that phenotypic traits are altered during the lifetime of organisms and then passed on to their offspring. This type of inheritance is often caused by environmental factors and doesn’t alter the underlying gene sequence.
What is Evolution?
An organism’s ability to adapt to its surroundings through changes in its genetic makeup over time is known as evolution. In other words, evolution is the process by which organisms change through time as a result of genetic variations. While evolution is a natural phenomenon, evolution is not the same as natural selection. Natural selection is a process that occurs within populations, whereas evolution refers to the changes in populations over time. In other words, natural selection occurs within a population, whereas evolution occurs between populations.
Processes of Evolution
- Natural Selection: This is a process in which organisms with certain genetic traits are more likely to survive and pass on their genes. For example, a certain allele that allows a species to be resistant to a certain kind of disease is selected in a population where that disease is common. Over time, that allele becomes more common in the population as more individuals with that allele survive than those without it.
- Genetic Drift: This occurs when a particular allele becomes more or less frequent in a population due to chance. For example, two individuals who are the only ones in their population to survive a disease outbreak could produce offspring with an allele frequency different from the original population.
- Mutation: Mutations are changes that occur in an organism’s DNA. These mutations occur naturally, and some of them can lead to beneficial traits like increased resistance to diseases.
- Migration: Over time, some populations may migrate to new areas. In some cases, these migrations can result in interbreeding two populations with different allele frequencies. This can lead to the allele frequencies in both populations changing over time.
- Flow: In some cases, members of a population may migrate to new areas and interbreed with the local population. This is known as gene flow, and it can lead to the allele frequencies in both populations changing over time.
Key Differences Between Heredity and Evolution
When considering the difference between heredity and evolution, it is important to understand the underlying principles of each concept. These two ideas may seem similar since both focus on how traits are passed down from generation to generation. However, a closer examination reveals that these two concepts actually have very different underlying mechanisms.
In the case of heredity, genetic information is passed directly from parents to offspring through DNA. Traits are controlled by continuous segments of DNA that code for specific genes or combinations of genes. This means that while some traits may be inherited from one parent or another, there is no real alteration or progression involved in this process. In contrast, the core premise of evolution is that organisms evolve and adapt over time due to natural selection and other environmental factors.
So, in essence, heredity concerns how genetic information is passed down unchanged from one generation to another, while evolution describes how organisms change and develop over time as they acquire new genetic information through mutation and cross-breeding. Thus while these two concepts have some similarities in terms of their focus on inheritance and adaptation, they are ultimately quite different in terms of their mechanism and overall scope. Let’s understand the differences readily:
- Heredity occurs within a species, and evolution refers to changes in a species over time.
- Heredity refers to the transfer of genes from parent to offspring, whereas evolution refers to changes in allele frequencies in a population.
- Evolution occurs in environments where organisms are exposed to different selective pressures, whereas heredity happens within the controlled environment of a living organism.
- Evolution is the process by which organisms change over time, whereas heredity refers to the process of passing traits from one generation to the next.
Now you know that the processes of heredity and evolution require changes in organisms throughout time. In humans, heredity refers to the genetic transmission of characteristics from one set of parents to the next. On the other hand, the term “evolution” is used to describe a wide variety of processes that result in changes in the frequency of alleles in a population of organisms. You can better grasp the biological environment around you now that you know heredity and evolution. We hope our Heredity and Evolution Class 10 CBSE Notes help you pass your exams with flying colours.