Principle of Inheritance and variation

Principle of  Inheritance and variation

Genetics

➢ Branch of biology that deals with the study of heredity and variations.

➢ The term genetics was given by William Bateson in 1906 who derived it 

from Greek word ‘genesis’ meaning to grow into or to become.

Heredity

➢ There is an old proverb that “like begets like”, that is all living organisms tend 

to produce young ones like themselves. 

➢ Heredity is the transmission of genetic characters from parents to their 

offspring.

Inheritance:

➢ It is actually the process by which characters or traits pass from one 

generation to the next. 

➢ An elephant always gives birth only to a baby elephant and not some other 

animal. 

➢ A mango seed forms only a mango plant and not any other plant.

➢ Thus the offsprings resemble their parents.

Variation

➢ It is the degree of differences in the progeny (offspring) and between the 

progeny and the parents. 

➢ The term variation is also used for a single difference in a trait.

Branches of genetics

1.transmission genetics:transmission of genes 

from one generation to 

the next.

2.molecular genetics:It deals with the structure 

and function of genes at a 

molecular level.

3.Population genetics:It deals with the application 

of Mendel’s laws and other 

principles of genetics to 

populations of organisms. 

Historical aspects

➢ Early agriculturists (8000–10,000 BC) knew that causes of variation are hidden 

in the process of sexual reproduction. 

➢ They successfully bred domesticated varieties from wild plants and animals 

through selective crossing and artificial selection.

➢ Chicken is the domesticated form of Wild Fowl.

➢ Sahiwal Cow of Punjab is domesticated form of an ancestral Wild Cow.

Premedian idea about Inheritance

➢ They are often called Theories of Blending Inheritance as they believed that 

characters of the parents blended or got mixed during their transmission to 

the offspring. 

Theories of blending Inheritance:

Moist vapour theory

➢ Pythagoras proposed that, during coitus (intercourse), moist vapours from all 

parts of a male’s body gave rise to a similar body in female’s womb. 

Fluid theory

➢ Aristotle suggested that male’s semen was highly purified blood and the 

female’s menstrual fluid was the female semen which is not as pure as male 

semen. 

➢ The two fluids combined during coitus. 

➢ Female semen provided ‘inert’ fluid for the formation of the embryo and male 

semen gave form and vitality to the embryo. 

Performation theory

➢ It says that the organism is already present, i.e., pre-formed in the sperm or 

egg in a miniature form called homunculus(little man). 

➢ Fertilization is required to stimulate its growth. 

➢ This theory was given by Swammerdam (1679) and advocated by Malpighi.

Particulate theory

➢ Maupertuis (1698 – 1757) considered that heredity is controlled by minute 

particles which come from all parts of the body to the reproductive organs. 

➢ An individual is formed when the particles from male and female combine. 

Kolreuter

➢ The first systematic studies of genetic crosses were carried out by Joseph Kölreuter

from 1761 to 1766.

➢ In crosses between different strains of tobacco plants, he found that the offspring 

were usually intermediate in appearance between the two parents. 

➢ This led Kölreuter to conclude that both parents make equal genetic contributions to 

their offspring.

Theory of pangenesis

➢ Darwin (1868) thought that every cell of the body produces a tiny particle 

called gemmule or pangene. 

➢ It contains both the parental characters and variations. 

➢ All the gemmules or pangenesis of the body cells collect in the gametes and 

are passed on to the zygote.

Theory of continuity of germplasm

➢ August Weismann (1892) proposed this theory. 

➢ According to this theory germplasm is ‘immortal’ and is passed from 

generation to generation. 

➢ Somatoplasm that forms the body is ‘mortal’ and perishes when the organism 

dies.

Gregor johann Mendel

➢ He grew up on a farm in Hynčice (formerly Heinzendorf) which was then a 

part of Austria and is now a part of the Czech Republic.

➢ As a young boy, he worked with his father grafting trees to improve the 

family orchard. 

➢ A rural upbringing taught him plant and animal husbandry and inspired an 

interest in nature.

➢ Mendel selected Garden pea (Edible Pea).

➢ Pisum sativum.

➢ Chromosome number 2n=14.

Humming bird

                                 The Humming bird

                                                                                  

The humming birds are  the smallest bird in the  kingdom  of the birds. The humming  birds are the native of america and constitute the biological family trochilidae. Their length is about 7.5 to 13 cm, the smallest extent bird species is of 5 cm (2.0) is also called the bee birds.

They are called as the humming bird because the humming sound created by their wings which flaps at high frequencies  audible to humans.

The humming  bird is the only bird which can fly back word  direction. The humming birds  had to sucks 2000 times nectar from the flower to complete their body needs.

Life span

Humming bird have a such a long life span with such a rapid metabolism. Though many die during the first year of the life, especially in the vulnerable period of hatching and fledgling, those who survive may live a decade or more. Among the better north american species the average life span is about 3 to 5 years. The longest living record of the humming bird is banded(ringed)  was an adult  at least  one year old, then recaptured 11 years old, making her at least 12 years old.

Reproduction

The humming bird do not take part in nesting. The most of the species make the cup shaped nest on the branches but few of them attach the nest to the leaves. Many humming bird species use the spider silk and lichens to make their nest secure the structure. The unique properties of the silk  allows the young ones grow better way. The two eggs are lay by the mother humming bird, it takes up to  14 to 23 days for incubation depending on the species , surrounding,temperature, and female attentiveness to the nest.

Bill evolution

Upon maturity, males of a particular species phaethornis longirostris the long billed  hermit, appears to evolving a dagger like weapon  on the beck tip as secondary sexual trait to defend meeting areas.

Migration 

Most of the humming birds migrate from america to spend the winter in mexico, the Caribbean island and north america. The south american species also move towards the north in to the tropics to spend the winters. A few species are year-round to the Florida,California and far to southern desert region US.

Diet and specialisation for food gathering

For nutrients the humming bird eat a variety of insects, including the mosquitoes, fruit fly and the gnats on the leaves and spider on their web. The lower beak of humming bird can bend up to 25 degree when it widen at base, making a large surface for catching the insects.

To supply the energy the humming bird drink the nectar , which is a fluid like substance present inside the flower in the small amount. Like bees humming  bird has the ability to access the amount of sugar from the nectar ; they mostly reject the flowers who has low sugar containing less than 10%

they only select the flowers which have more sugar content.

More images of humming bird:

  

Beautiful flowers

      The top most beautiful flowers

1.cherry blossom

2.lilly of the valley

3.Sunflower

4.Rose

5.Gazania

6.bleeding heart

7.pulmeria

8.Dahliya

9.Bird of paradise

10.Tulips

Hardy Weinberg principal

           Hardy Weinberg principal

➢ It was proposed by G.H. Hardy, an English mathematician and W. Weinberg, 

a German physician independently in 1908. 

➢ It describes a theoretical situation in which a population is undergoing no 

evolutionary change. 

➢ In fact, it defines the genetic structure of a non-evolving population. 

➢ Mutations introduce new genes into a species resulting a change in gene 

frequencies.

➢ Gene frequency is the frequency with which a particular allele occurs in a 

population.

➢ If certain conditions existed, gene frequencies are supposed to remain fixed 

and even remain the same through generations.

➢ This is called genetic equilibrium.

Essential condition HWP

No mutation:

➢ Sudden appearance of variations are called mutations.

➢ There should not be either gene or chromosomal mutation. 

No gene flow:

➢ Gene flow refers to the movement of alleles from one population to another 

as a result of interbreeding between members of the two populations. 

➢ The removal of alleles from one population or addition of alleles into another 

population is called gene flow or gene migration. 

➢ There must not be gene flow between the population.

No genetic drift :

➢ Genetic drift is also known as “Sewall Wright Effect”.

➢ It occurs only by chance. 

➢ It is non directional. 

➢ Genetic drift can cause elimination of certain alleles or fixation of the other 

alleles in the population.

No genetic recombination:

➢ The alleles of parental linkage groups separate and new associations of 

alleles are formed in the gamete cells.

➢ This process is known as genetic recombination.

➢ Crossing over during meiosis is a major source of genetic variation within 

population.

No Natural selection:

➢ There must be no natural selection pressure with respect to the alleles in 

question.

Mathematical expiration

➢ Individual frequencies of alleles may be named p, q etc. 

➢ In a diploid p and q represent the frequency of allele A and allele a.

➢ The frequency of AA individuals in a population is p

2

. 

➢ The probability that an allele A with a frequency of p appears on both the 

chromosomes of a diploid individual is the product of the probabilities i.e., p2

. 

➢ Similarly of aa is q2

, of Aa is 2 pq.

➢ Thus p

2 + 2 pq +q2 =1. 

➢ This is a binomial expansion of (p + q)2

. 

➢ It is possible to calculate all allele and genotype frequencies using the 

expressions

○ Allele frequency p + q = 1.

○ Genotype frequency p2 + 2pq +q2 =1.

➢ Constant gene frequencies over several generations indicate that evolution is not 

taking place. 

➢ Changing gene frequencies would indicate that evolution is in progress. 

➢ In other words, evolution occurs when the genetic equilibrium is upset.

➢ Evolution is a departure from Hardy-Weinberg Principle.

The Asiatic lion

                                     The Asian lion

                                              

The Asiatic lion is found in India in Gir  national park and environs in the Indian state of Gujarat.The Asiatic lion are Endangered species which have the population of only five hundred and it is  increasing day by day,In the starting they were only the 20 left lions in the Gir national park after when the government had taken the action to save the lion they are increasing day by day not only in the Gujarat  now the lions  are found in the different part of India in zoo and century  in India to grow there population.

The lions of India are the tourist spot for the people as peoples from many country come to India  to see and research on the Asiatic lion.The lions are spreading and increasing day by day so they need more land to grow and populate them as for this the government is transporting the lions to the different part of the country.

The Asiatic lion is the rare species of India which were one  of the five pantherine cats inhibits in India among with the Bengal tiger,India leapord, snow leapord , and the clouded leapord. The Asiatic lion is also known as the "Indian lion " or "persian lion".

In some cases the Asiatic lion is killed by some people for money illegally , killing the lion is crime in India for this any people can get a big punishment.

Reproduction

The Asiatic lion  foremost between September and January mostly. Mating happens between three to six days. In this days they do not hunt or do not drink water. Gestation lasts about 110 days. The female lion mostly give birth to one or four lions. The average interval of the lions baby were 24 months in this time they to survive or they will die, the most reasons for the death of lions cubs are killed by other lions or by the diseases or injury. The cubs become Independent at the  age of two years. The adult male leave their mothers and make them own territory .

The lions are also the symbol of the god in the Hindu  religion as the royal vehicle of  many goddess. The  lion are loyal to humans they did not kill the humans without any reasons. The lion is also called as the king of the jungle as no one animal is royal and powerful then the lions. The lions are also so intelligent animals because they had a great Technic to hunt in the group or in a single form.  

some beautiful image of lions

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The Asian Elephant

                                    The Asian Elephant

                                                

The Asian Elephant is called as the Asiatic Elephant.It is the only living species of genus Elephas and they are distributed through the Indian subcontinent  and south east Asia, India in the west, Nepal in north, Sumatra in south, Borneo in the east.

The Asian Elephant can leave the life of about 60 to 70 years but some Elephant can leave up to the life span of 100 years or more.The Asian Elephant is the largest living animal in Asia. The Asian Elephant are listed in endangered species on the   IUCN red list, as there population are has decreased about 50% , the reason fort the decrease in the population of Asian elephant is they are losing there natural habitat and there birth rate is less and the death rate is more, the Elephant are also killed for there teeth because there teeth are so valuable, different types of rare medicine are made  from them and they are also used as the decoration peace in the houses of rich people this is one of the most reason why Elephant are killed.

The Asian Elephant are very humble and loyal to human being as they were known as the symbol of god in Hindu religion as the Avatar of  lord  Ganesha. The Elephant were used in the battle field by the kings army to win the battle as they were big in size and were so strong as a single elephant can kill up to 100 to 200 peoples in the battle field.The Elephant was the royal vehicle of lord Indra in Hindu religion which was so big and beautiful and he was white in color and his name was Airavata, it was also called as 'abhra-matanga' as the Elephant of clouds,'Naga-malla' the fighting Elephant.

 

Size

On average, males are about 2.75 m (9.0 ft) tall at the shoulder and 4 t (4.4 short tons) in weight, while females are smaller at about 2.4 m (7.9 ft) at the shoulder and 2.7 t (3.0 short tons) in weight. Length of body and head including trunk is 5.5–6.5 m (18–21 ft) with the tail being 1.2–1.5 m (3.9–4.9 ft) long.The largest bull elephant ever recorded was shot by the Maharaja of Susang in the Garo Hills of Assam,India in 1924, it weighed 7 t (7.7 short tons), stood 3.43 m (11.3 ft) tall at the shoulder and was 8.06 m (26.4 ft) long from head to tail.There are reports of larger individuals as tall as 3.7 m (12 ft).

Domestication

The first historical record of the domestication of Asian elephants was in Harappan times. Ultimately, the elephant went on to become a siege engine, a mount in war, a status symbol, a beast of burden, and an elevated platform for hunting during historical times in south Asia.

Elephants have been captured from the wild and tamed for use by humans. Their ability to work under instruction makes them particularly useful for carrying heavy objects. They have been used particularly for timber-carrying in jungle areas. Other than their work use, they have been used in war, in ceremonies, and for carriage. It is reported that war elephants are still in use by the Kachin independence army (KIA) to take control of Kachin state in northern Myanmar from Myanmar's military. The KIA use about four dozen elephants to carry supplies. They have been used for their ability to travel over difficult terrain by hunters, for whom they served as mobile hunting platforms. The same purpose is met in safaris in modern times.

Some beautiful picture of Elephant

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