Question

I need heredity and various chapter notes exclude deducted topic.....
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Answer 1

Explanation:

CELL IS THE BASIC STRUCTURAL AND FUNCTIONAL UNIT OF LIFE . ON BASIS OF WELL DEVELOPED NUCLEUS ORGANIMS ARE DIVIDED INTO Prokaryotes & Eukaryotes . EUKARYOTES ARE FUTHER DIVIDED TO Unicellular and Multicellular . MULTICELLULAR ORGANISMS FURTHER DIVIDED INTO Autotrophs and Heterotrophs ON THE BASIS OF PHOTOSYNTHESIS. HETEROTROPHS ARE DIVIDED INTO Endoskeleton and Exoskeleton ON BASIS OF LOCATION OF SKELETON.

Answer 2

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Heredity

• The process by which the features of an organism are passed on from one generation to another is called heredity.
• The process is done by genes, which define the characters in the organism.

Mendel’s work

• Gregor Johann Mendel, known as ‘Father of Genetics’, was an Austrian Monk who worked on pea plants to understand the concept of heredity.
• His work laid the foundation of modern genetics.
• He made three basic laws of inheritance – The Law of Dominance, The Law of Segregation and The Law of Independent Assortment.

Dominant traits

• The traits that express themselves in an organism in every possible combination and can be seen are called Dominant traits.
• In Mendel’s experiment, we see that tall trait in pea plants tends to express more than the short trait.
• Therefore, the tall trait of the plant is said to be dominant over the short trait.

Recessive traits

• A trait which is not expressed in the presence of a dominant allele is known as recessive.
• So, recessive character/trait is present in an organism but cannot be seen if a dominant allele exists.

Monohybrid cross

• When only one character is considered while crossing two organisms, then such a cross is known as monohybrid cross.
• The ratio of characters, arising out of this cross, at F2 generation is called monohybrid ratio.
• E.g., If tall plant (TT) is crossed with a dwarf plant (tt), we get 3 tall:1 short plant at the end of the F2 generation.
• So, 3:1 is monohybrid ratio.
• Here, the height of the plant is considered at a time.

Dihybrid cross

• When two characters are considered while crossing two organisms, then such a cross is known as a dihybrid cross.
• The ratio of characters, arising out of this cross, at F2 generation is called dihybrid ratio.
• E.g., If a plant with round and green pea is crossed with a plant with wrinkled and yellow pea,
• The first generation plants would all have round and green pea.
• On crossing the same for an F2 generation, we would observe four combinations of characters in the ratio of 9:3:3:1.
• Thus, 9:3:3:1 is the dihybrid ratio.

Laws of Mendel

• Law of Dominance says that a gene has two contrasting alleles and one always expresses itself in the organism.
• It is called the dominant gene and it expresses in any possible combination.
• Law of Segregation says that traits get segregated completely during the formation of gametes without any mixing of alleles.
• Law of Independent Assortment says that the traits can segregate independently of different characters during gamete formation.

Sex determination

• The process of determining the sex of an individual, based on the composition of the genetic material is called sex determination.
• In different animals, sex of an embryo is determined by different factors.
• In humans, sex determination happens on the basis of the presence or absence of Y chromosome.
• XX is female and XY is male
• An ovum always contains X chromosome.
• An ovum, upon fusion with Y containing sperm, gives rise to a male child and upon fusion with X containing sperm gives rise to a girl child.

Acquired characters

• The traits that are acquired by an organism over the period of its lifetime are termed as acquired characters.
• These characters may or may not get transferred to the next generation.

Inherited characters

• The traits that are inherited from the parents are called inherited characters.
• These traits always get transferred to the next generation, but depending on the dominance or recessiveness it may or may not be expressed.
• Examples are height, skin colour and eye colour.

Genetic variations

• The differences in the DNA sequences among every organism leading to the diverse gene pool are called genetic variations. These differences lead to different/varied physical characters or biochemical pathways.

Natural selection

• It is the phenomenon by which a favourable trait in a population of a species is selected.
• Changing natural conditions exert equal pressure on all the existing species.
• The species/organisms which are better adapted to the changing conditions survive and reproduce i.e. selected by nature and species/organisms which cannot adapt perish i.e. rejected by nature.

Speciation

Genetic drift

• Natural selection can play an important role in deciding the traits that survive in a population. However, random fluctuations in gene variants are seen on many occasions. This phenomenon is known as genetic drift. Thus, genetic drift is a change in the frequency of an existing allele in a small population.
• Genetic drift may cause a gene variant to disappear from the population and thus reduce genetic variation.

Speciation

• It is the process of formation of a new species from existing ones due to several evolutionary forces like genetic drift, isolation of populations, natural selection, etc.  Speciation leads to diversity in the ecosystem and the diversity and diversity lead to evolution.