Science [2 Mark Questions]

Acquired traits are structural, functional and behavioural changes that an individual develops during its life time. due to particular environment trauma use and disuse etc the changes which are acquired do not happen in reproductive cells they just happen in somatic cells. the removal of tails is a acquired trait which is not passed on to DNA of germ cells. They remain restricted to somatic cells. They are destroyed with the death of the mice. Hence the new generation continue to have tails.

A species is a population of organisms consisting of similar individuals which can breed together and produce fertile offspring’s.
Plant species: Wheat, Paddy, Sunflower etc.
Animal species: Cat, Dog, Tiger, etc.

Four modes of asexual reproduction are:-

1. Binary Fission: In binary fission, a single cell divides into two halves. Some of the organisms that divide by binary fission are bacteria and Amoeba.
2. Budding: It involves the formation of a new individual from a protrusion called a bud. It is very common in plants, yeasts and lower level animals such as Hydra.

In Hydra, cells divide rapidly at a specific site and develop as an outgrowth called a bud. This bud, while attached to the parent plant, develops into a small individual. When this individual becomes large enough, it detaches itself from the parent body to exist independently.

3. Multiple Fission: In multiple fission, a single cell divides into many daughter cells simultaneously, for example, Plasmodium.
4. Fragmentation: Fragmentation is the unintentional cutting up of the body of an organism in which each part grows into a different organism. It is most commonly seen in some annelids and fungi.

Forelimb of humans and forelimb of lizard are the homologous organs and the wing of insect and the wing of bird are analogous organs.

The depth appears to be less because of refraction of light. Light coming from the bottom of the bucket gets refracted and we percieve the depth to be lesser.
Consider the following example.
The light coming from the coin placed at the bottom gets refracted away from the Normal because of refraction.

So, instead of appearing at its real depth, it appears raised. The same phenomenon is applicable to the bottom of the bucket itself. Hence, the bottom appears raised and we see that the bucket is filled slightly less than it actaully is.

No, depending on the nature of variations different individuals have been different kinds of advantages. However, when a drastic change occurs in environment, only those organisms in the population will survive which have an advantageous variation in that population to survive in changed environment.

Charles Darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".
Natural selection is a nature’s phenomenon in which the species which inherits variations and has better chances of survival are allowed to reproduce and produce a large number of off springs.

When different animals which have organs originated from the same part of the body but function differently then they are known as homologous organs.
Example: Wings of a bat, wings of birds, dolphin, flipper and human arm are the homologous organs. They all are derived from the same set of bones which are humerus, radius, ulna, carpals, metacarpals, and phalanges. But all of them function differently.

The process in which new species are formed from the preexisting species is known as speciation.
Yes, traits like eye colour or height is genetically inherited because they can be passed on from one generation to the next. whereas physical strength is the acquired trait, the one acquired over a course of time.

The presence of homologous organs in different animals provides evidence for evolution by telling us that they are derived from the same ancestor who had the ‘basic design’ of the organ on which all the homologous organs are based.

Natural selection is the process of evolution of a species whereby characteristics which help individual organisms to survive and reproduce are passed on to their offspring, and those characteristics which do not help are not passed on.

For a trait of an organism to be inherited, it should bring about a change in the genes present in the reproductive cells or gametes of that organism. The traits acquired during the life time of a person do not bring about a change in the genes present in its reproductive cells or gametes and hence they are not inherited by the offsprings.

The forelimbs of humans and the wings of birds look different externally but their skeletal structure is similar. It means that their origin is similar (as wings in birds are modifications of forearm) but functions are different - the wings help in flight whereas human forearm helps in various activities.

Bacteria have better body design because it has so much variation to adjust in different climatic condition.

1.  

1. E is recessive.
2. E is dominant.

2. The colour of their eyes is brown.
3. Combination ee will produce children with blue eyes.
4. Combination EE or Ee will produce children with brown eyes.

Wild cabbage, which is the common ancestor of broccoli, cauliflower and cabbage.
Various plant parts of Wild Cabbage (Brassica Oleracea) are modified by artificial selection to give broccoli, cauliflower and cabbage. Thus, Wild cabbage includes the other three.

Human evolution has been studied by using the various tools of tracing evolutionary relationships like excavating (digging earth), carbon-dating, studying fossils and determining DNA sequences.

Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy (XY).

1. The gene for red petals is dominant, while the gene for white petals is recessive.
2. The gene for red petals can be represented by R and the gene for white petals can be represented by r.

Brown hair color genes are dominant and the red hair color genes are recessive ; The genotype of brown hair is BB (dominant always represented by capital letter) and that of red hair bb (Recessive represented by small letter)

Individuals with a particular trait may increase in a population as a result of the following:

• Natural selection: When that trait offers some survival advantage.
• Genetic drift: When some genes governing that trait become common in a population.
• When that trait gets acquired during the individual's lifetime.

The chromosomes which determine the sex of a person are called sex chromosomes. There are two types of sex chromosomes? X and Y chromosomes.

According to Mendel’s first law of inheritance: The characteristics (or traits) of an organism are determined by internal ‘factors’ which occur in pairs. Only one of a pair of such factors can be present in a single gamete.

1. Combination Bb will give brown eyes.
2. Combination bb will give blue eyes.
3. Combination BB will give brown eyes.

Human females have two X chromosomes whereas the human male has one X and one Y chromosome.
Thus females are homogametic.

Recessive trait is expressed only when the recessive alleles are present in a homozygous condition, i.e. that the individual has both the alleles as recessive alleles.
When di-Hybrid cross is conducted between two heterozygous parents with contrasting traits then it produces offspring which are 3 dominant and 1 recessive.
Tt × Tt = TT, Tt, Tt, tt
the ratio would be - 1 : 2 : 1

Geographical isolation is the major factor in the speciation of sexually reproducing animals because it interrupts the flow of genes between their isolated populations through the gametes.

1. Tall: Tt will have tall plants because of the presence of T which is dominant gene and t is recessive gene.
2. Dwarf plants: It is dwarf due to the presence of both the recessive genes.
3. Tall plants: These plants are tall due to the presence of both the dominant genes.

Genes are the units of heredity which transfer characteristic from parents to their offspring’s during reproduction. Genes are located on the chromosomes.

Traits are expressed in the form of genotypes and phenotypes. Proteins are responsible for the traits. Traits are expressed in the form of proteins. Traits exhibited can be represented by genotype and phenotype of an individual. Genotype is the internal genetic constitution of a particular trait. Phenotype is the physical character that is expressed in the form of a trait.

The first step in sexual reproduction is gamete formation. In this step, the number of chromosomes gets halved. Thus, each gamete receives half the number of chromosomes to that of somatic cells. During fertilisation, the fusion of male and female gametes takes place, which results in the number of chromosomes in the zygote to be equal to that of somatic cells. Thus, the chromosomal number of the sexually producing parents and their offspring is the same.

When the object is placed between pole and focus of the concave mirror, the image formed is virtual, erect and magnified.

In sexual reproduction gametes undergo meiosis which introduces variation by recommendation crossing over, fertilization of gametes also introduces variation. Off springs genetic material varies from the parents & thus inheritance of traits in sexual reproduction introduces variations in species.

Bacteria have simpler body plan when compared with human beings. Both of them have evolved differently. Bacteria can inhabit most of the unfavourable habitats such as hot springs, deep- sea thermal vents and the ice in Antarctica.

Natural selection, genetic drift and acquisition of traits during the life time of an individual can give rise to new species.

The process by which different characters are passed on from the parent to the progeny is known as inheritance. The rule of inheritance of such traits in human being are related to the fact that both father and the mother contribute practically equal amounts of genetic material to the child. This means that each trait can be influenced by both paternal and maternal DNA. Thus, for each trait there will be two versions in each child.

Biodiversity refers to all the diverse plants, animals and micro organisms present on earth.
Biological diversity or biodiversity is the occurrence of diverse or varied forms of living beings which differ from one another in external appearance, size, colour pattern, internal structure, nutrition, behaviour, habitat, etc.
There are various categories of classification. These are:

Genes are simply short regions of DNA which code for either a protein or RNA molecule. In eukaryotes, genes are mostly found in the nucleus of the cell, but some (13 in humans) are also located in the cell's mitochondria, in mitochondrial DNA.

The advantages of sexual reproduction:

• It produces variation in the off spring.
• The species can adapt to new environments due to variation, which gives them a survival advantage.
• A disease or change in environment is less likely to affect all the individuals in a population.

Genetic variation in a population describes the existence in that population of different alleles, or alternative forms, for a given gene. The presence of genetic variation implies that individuals of the population vary in the alleles they possess, meaning that individuals differ in genotype.

1. Characters that are passed on from parents to offspring are inherited characters. For example, colour of seeds, colour of eyes, etc.
2. Characters appearing in an individual’s lifetime but cannot be transmitted to next generation are acquired characters. For example, obese body, loss of a finger in an accident, etc.

Acquired	Inherited
The acquired traits are the traits which are experienced by an individual during his life time. The acquired traits of an organism cannot be passed on to its future generations. For e.g., 'low weight' of beetle. ' cut tail' of a mouse.	Inherited traits are distinguishing qualities or characteristics which one acquires from the ancestors. The inherited traits of an organism are passed on to its future generations. For e.g., red colour of beetles, fur coat of guinea pigs.

Mendel choose pea plants for studying inheritance because pea plants had a number of clear cut differences which were easy to tell apart. Another reason for choosing pea plants are they were self pollinating and many generations can be produced in a short time span.

No, because mother has a pair of X chromosomes. All new born babies will inherit an Xchromosome from mother whether they are baby boys or baby girls.

During sexual reproduction two different parent i.e. male and female take part as a result of which the newly formed zygote possess genetic material of both parents. It leads to interchange of genetic information between two gametes which is passed to the progeny and develops variation.

DNA is present on chromosomes, and genes are segment of DNA. Hence they are indirectly related. They both contain genetic material of the parent and passed on to the progeny. Thus we can say that they both have similar behaviour.

Analogous organs: Such organs which perform similar function but are different in structure and origin are called analogous organs. Example - Wings of birds and wings of insects.
Homologous organs: Such organs which may have different functions but similar structure and origin are called homologous organs. Example - forearm of frogs, lizards and birds.

Geographical isolation will not be a major factor in the speciation of a self pollinating plant because it does not depend on other plants for its process of reproduction to be carried out.