Heredity And Evolution

Sexual Reproduction brings about maximum variations in the offspring because it involves fusion of gametes thus causing variations whereas asexual reproduction does not involves fusion of gametes so the offspring inherits genes from one parent only and thus variation is rare.

Some humans have attached earlobes while some have few earlobes which is due to variation in genes.

Gametes form the link between one generation and the next because the hereditary information is present in the sex cells (gametes), Gametes pass on the parental (mother and father) traits to the offspring.

These internal factors are known as genes. Genes are found in pairs on chromosomes and they carry traits from parents to the offspring.

Gene pair can be represented as Tt. T-Tallness-T and Dwarfness-t.(Dominant is always represented with a capital letter and recessive with a small letter).

These are known as the sex chromosomes. Females have XX as the set of sex chromosome whereas males have XY as the set of sex chromosome

Sperm decides the sex of the child. During fertilization if X of the sperm fertilizes with egg (having one X chromosome) a girl child is born; if Y of the sperm fertilizes with egg a boy child is born.

The sex of an infant is not a case of inheritance of characteristics.

False, sex of an infant is case of inheritance of characteristics. Inheritance of characters determines the sex of an infant.

The new born child will be a baby boy. The unfertilized egg has one X chromosome; the sperm either carries a X chromosome or a Y chromosome. If X of the sperm fertilizes with the egg the child born will be female (XX), and if Y of the sperm fertilizes with the egg the child born will be male (XY). Thus the new born child with an XY pair of chromosome will be a baby boy.

The Combination XY produces a male child. The unfertilized egg has one X chromosome. The sperm either has a X chromosome or a Y chromosome. Male child will be produced if sperm carrying Y chromosome fertilizes with the egg. Female child will be produced if sperm carrying X chromosome fertilized with the egg. Therefore, combination XY will produce a male child.

Gregor Johann Mendel studied the inheritance of traits from one generation to the next. He discovered basic principles of heredity through his experiments on pea plant.

Mendel used pea plant for conducting experiments on inheritance. Reasons for selecting pea plant were

a) they are easy to raise

b) give many offspring per mating

c) self-fertilization

d) have varieties in genotype and phenotype.

Black hair color; it is because gene for black hair color is dominant so it will be expressed and since gene for red hair is repressive so it will be suppressed under the influence of black hair gene.

The four blood groups in humans are blood group A, B, AB and O. The ABO blood group system was given by Karl Landsteiner in 1900. He identified the blood types O, A and B.

(a) Incubation of eggs Lizard (Agamaagama) at high temperature produces male progeny.

(b)Incubation of eggs of Turtle (ChrysemaPicta) at high temperature produces female progeny.

(a) Pair

(b) Recessive; Dominant.

(c) Free; Attached.

(d) 23; 46

(e) Same

(f) Sex; Female; Male.

Marine arthropods whose fossils have been studies are known as Trilobites.

Ammonites are the extinct molluscs with flat, coiled spiral shape shell millions of years ago but are now extinct.

Carnivorous animals that appeared about 250mya and disappeared 65 mya are none other than Dinosaurs, as we all know dinosaur disappeared 65mya.

So, X- Trilobites; Y- Ammonites; Z- Dinosaurs.

(a) X- Wild Cabbage (Brassicaoleracea) is made to produce 5 different varieties of vegetables by artificial selection.

(b) These 5 different looking vegetables are Cabbage, Kohlrabi, Kale, Broccoli, and Cauliflower.

(c) The process of evolution involved in this example is known as Artificial Selection. Artificial Selection is the intentional reproduction of individuals having desired characteristics.

(a)Animals A, B, C, D and E could be sparrow, Lizard, human, frog, insect.

(b) Forelimbs of Bird, lizard, human and frog are called homologous organs because their basic structure of bones is similar but they perform different functions. This means that they have had a common ancestor and with time they adapted themselves according to the requirements.

(c) The existence of homologous organs in animals A, B, C, D tell us that since they have similar basic structure of origin, they have a common ancestor.

(d) Modified forelimbs of Bird and wings of Insect are called analogous organs because they have different basic structure but they perform similar functions. Bird uses its forelimbs to fly; similarly insect uses its wings to fly. Because their basic structure of origin is different so they do not have a common ancestor.

(e) No, Animals having analogous organs do not have a common ancestor because their basic structure of origin is different.

(a) Bird, lizard and dinosaur; Birds can fly ; Lizards can walk on walls; Dinosaurs can fly as well as walk too)

(b) Homologous organs. (Organs that have same structure but different function)

(c) Feathered Wings as in birds

(d) Tail as in reptiles

(e) YZ X?

(a) Yes; the change in color of beetle is a process of evolution which might have occurred to adapt to certain environmental condition.

(b) Yes; the color of green beetles can be passed on to the next generation through genes.

(c) The green color will protect the beetle from predation as it will help the beetle hide in the bushes.

(d) Yes; it involved a change in genetic material because unless and until the gene responsible for color gets some changes, no new color can be produced than the original one.

(a) These organs that have different basic structure but perform similar functions are known as analogous organs. So organs P and Q are analogous organs.

(b) Wings of a Butterfly and wings of a sparrow; wing of an insect and wing of a bird.

(c) These organs that have similar basic structure but perform different functions are known as homologous organs. So organs R and S are homologous organs

(d) Forelimbs; Forelimbs of a frog and forelimbs of human are homologous.

Tt- represents tall plant. This is because T is dominant so it is expressed and since t is recessive, it gets suppressed. (Where T=tall plant; t= dwarf plant)

tt- represents dwarf plant. This is because both the genes for determining the height of the plant are recessive and none of the dominating genes are present.

TT- represents tall plant. This is because T is dominant gene for height and both the dominant genes are present.

There are equal possibilities of the daughter having blood group O and B.

Blood group O will have O and O genes whereas blood group B will have B gene as dominant and O as recessive so the gene pairs that could be formed will be either O and B or O and O ; either B and O or O and O. Hence the equal possibility i.e. 50-50.

(A) Gregor Johann Mendel gave the laws of inheritance. He studied heredity on pea plants and gave three laws of inheritance. 1. Law of Dominance. 2. Law of segregation. 3. Law of independent assortment.

(B) Snail can change sex amongst its individuals. It is usually done among the endangered snail species in order to keep themselves Alive. This indicates that genes do not play a role in determining the sex of the individual.

Genes are the units of heredity i.e. they transfer characteristics from parents to offspring and determine the characteristics of the offspring. Example- Transfer of hair color from parents to the offspring. Let’s say that the mother has dominant genes for black hair, (BB gene constitution) and the father has recessive gene for blonde hair (bb gene constitution). When fertilization will occur the mother will transfer one B gene for black hair to the zygote and the father will transfer one b gene for blonde hair to the zygote. The resulting offspring will have Bb gene for hair where B is a dominant gene and b is a recessive gene. Since B is dominant it will be expressed and b will be suppressed, the child will have black hair.

(A) Variations are heritable differences within individuals of a species. Advantage- Nature always selects the fittest organism so if no variation occurred in genes there would not have been so many species of the organism. In a changing environment, variation always increases the chances of survival of a species.

(B) Sex chromosomes are a pair of chromosome that decide/determine the sex of an individual. The 23^rd pair of chromosome is Allosome (or sex chromosome).

There are 2 sex chromosomes (one pair). X and Y chromosome. Y chromosome is found only in males. X chromosome is found in both male and female

The unfertilized egg has one X chromosome. The sperm either has a X chromosome or a Y chromosome. If sperm carrying Y chromosome fertilizes with the egg, male baby will be born with the genetic constitution XY. But if sperm carrying X chromosome fertilized with the egg, female baby will be born with the genetic constitution XX.

(a) TT – Tall plant (T is a dominant gene).

(b)tt- dwarf plant (t is a recessive gene and there is no dominant gene to rule over it so dwarf height).

(c)XX- Female. (Female have both the sex chromosome as X X).

(d)XY- Male. (Male have One X chromosome and the other is Y chromosome as their sex chromosome).

(A) In the F1 generation we will get all tall plants with Tt gene combination and in the F2 generation we will get 3 tall plants (TT/Tt) and one dwarf plant (tt).

(B) This is an example of a monohybrid cross because there is just one trait i.e. height whose inheritance pattern is being studied.

It is a monohybrid cross. A monohybrid cross is a cross between two individuals with two different alleles on one gene. It produces a phenotypic monohybrid ratio of 3:1 in the F2 generation. Whereas a Dihybrid cross produces a phenotypic Dihybrid ratio of 9:3:3:1 in the F2 generation.

For example- When pure tall plant (TT) are crossed with pure dwarf plants (tt), the offspring of the F1 generation is all tall plants (Tt). When these Tall plants cross bred with each other, they produce ‘TT’ ‘Tt’ ‘Tt’ ‘tt’ offspring i.e. tall : short = 3:1. The phenotypic monohybrid ratio in the F2 generation is 3:1.

(A) Dwarf-ness is denoted by letter ‘t’ . For plants that have always produced dwarf offspring, the genotype will be ‘tt’ as dwarf-ness will only be expressed when both the genes are recessive i.e. ‘tt’

(B) Tallness is denoted by letter ‘T’. For plants that have always produced tall offspring, the genotype will be TT. It can also be Tt because since dominant gene T is present it will not let the recessive trait i.e. dwarf-ness express itself.

(C) (i)Genotype of dwarf plants will be ‘tt’ because dwarf-ness is a recessive trait that is expressed only when both the genes are recessive.

(ii)Genotype of tall plant will be ‘TT’ because the parental cross is producing tall offspring always.

(A) (i) sperm cell will have 23 chromosomes as gametes consist of half the number of chromosome of somatic cells.

(ii) Zygote will have 46 chromosomes as 23 chromosomes from the gamete of mother (egg) and 23 chromosome from the gamete of the father (sperm) will fuse to a total of 46 chromosomes.

(b) When both parents have same genes Tt and Tt and they are made to cross bred, we get a phenotypic ratio of 3:1 of tall: dwarf. (TT, Tt, Tt, tt)

(a) 46 (23 pairs of chromosome)

(b) 23 chromosomes (haploid)

(c) 23 chromosomes (haploid)

(d) 46 chromosomes (23 pairs of chromosome)

(e) 46 chromosomes (since it is fertilized by the sperm)

(a) This factor is known as Genes. They are unit of heredity transferred from parents to offspring. Each parent has a gene pair in each cell for each trait studied. One member of the gene pair segregates into a gamete, thus each gamete only carries one member of the gene pair and hence only one out of a pair of contrasted characters is represented in a gamete by its gene.

(b) These internal factors known as genes are found on chromosomes which are made of DNA and protein and found in the nucleus of the cell.

No, the genetic constitution of mother does not play a significant role in determining the sex of baby. This is because mother has 2 X sex-chromosomes (i.e. XX) so the baby will inherit an X chromosome from the mother. It is the father whose genetic constitution plays important role. Father has XY sex chromosomes so the baby will either inherit X chromosome or Y chromosome through sperm. If the sperm carries X chromosome the baby born will be a girl (XX) and if the sperm carries Y chromosome the baby born will be a boy (XY).

(a) Green seed is the contrasting trait of yellow seed where Green is recessive and yellow is dominant.

(b) Wrinkled seed is the contrasting of round seed where Wrinkled is recessive and round is dominant.

(A) Heredity refers to passing on of traits/characters genetically from parents to offspring.

The units of heredity are genes which are found on chromosomes. Chromosomes are organized structures of DNA and protein and are found in the nucleus.

(B) Mendel’s first law of inheritance is Law of Segregation which states that gene determines the characteristics/traits of an organism which always occur in pairs. One member of the gene pair segregates into a gamete.

(A) Mendel choose pea plant for conducting his experiments on inheritance because they are easy to raise and are self-pollinating too. Also many generations can be produced in a lesser time.

(B) Mendel’s second law of inheritance is also known as law of independent assortment which states that in inheritance of more than one pair of traits in a cross simultaneously, the factors responsible for each pair of traits are distributed independently to the gametes.

(A) The difference between groups of organism of any specie that is brought about by genetic differences is known as variation.

(B) Human height (Tall or dwarf) and Ear lobe (free or attached) show variations in human.

(C) Nature always selects the fittest organism so if no variation occurred in genes there would not have been so many species of the organism. Variation always increases the chances of survival of a species in a changing environment. For example- bacteria having heat resistant trait will survive when temperature rises too much, and bacteria that do not have this heat resistant trait will die when temperature in their surrounding rises too much.

(A) Genes are the units of heredity that transfer characteristics/traits from parent to offspring. They are found on chromosomes in our body and chromosomes are found in nucleus of the cell.

(B) A dominant gene is a gene that is expressed or appears in an organism in the presence of any another gene. Whereas, a recessive gene is a gene that is suppressed in an organism (doesn’t appears) in the presence of a dominant gene. A recessive gene is expressed or appears in an organism only if the other gene present is recessive.

Example- Height in Pea plant. Tall Plants may have gene combination of TT or Tt. (where T is a dominant gene). Dwarf plants will only have gene combination of tt(where t is a recessive gene)

(C) Genes are unit of heredity transmitted from parents to offspring. Each parent has a gene pair in each cell for each characteristic studied. One member of the gene pair segregates into a gamete, thus each gamete only carries one member of the gene pair from each parent and hence only one out of a pair of contrasted characters is represented in a gamete by its gene. When sperm fertilizes the egg, they form a zygote which develops to an organism having characteristics from both the parents which it would have inherited in the gametes through segregation.

(A) In his experiment with Pea Plant, Mendel crossed pure tall plants (TT) with pure dwarf plants (tt) and he obtained all tall plants in the F1 generation (Tt) which suggested that only one of the traits of parental plant showed in the F1 generation i.e. tall.

He crossed these tall plants of F1 generation amongst each other and obtained tall and dwarf plants in the ratio of 3:1 as the second generation (F2 generation). So he observed that the dwarf trait that had disappeared in the F1 generation reappear in the Second generation (F2 generation). Thus this shows that the traits may be dominant or recessive.

F2 generation- 3 tall:1 dwarf (Tt:tt)

(B) Mendel performed another experiment with Pea plants, this time taking two traits into consideration, yellow round seeds and green wrinkled seeds. He crossed these two plants and in the F1 generation and obtained all yellow round seeds. Yellow and round were dominant so they were expressed and Green and wrinkled were recessive so they remain suppressed. He self-pollinated these F1 generation plants to produce F2 generation and found yellow round seeds, green wrinkled seeds. Also he found yellow wrinkled seeds and green round seeds. Thus this experiment showed that the traits are inherited independently.

F₁ generation

Filial Generation of the offspring of parental (mother and father) type. Filial means offspring of a cross.

Dihybrid Cross.

Cross between two individual involves two pairs of heterozygous genes giving a ratio of 9:3:3:3 (theoretical).

Pea Plants

Mendel selected pea plants because they are easy to raise, they give many offspring per mating; they fertilize on their own and have varieties in genotype and phenotype

Male

Sperm with Y chromosome fertilizes with egg (having one X chromosome) thus producing a male with XY pair of chromosome.

Genetics

Heredity is passed on through genes.

Part of a chromosome that transmits a trait

Gene is present in pairs on chromosome and they transmit characteristics to offspring from parent.

23

Somatic cells have 46 chromosomes (23 pairs of chromosome) i.e., they are diploid. The chromosome number is haploid in sex cells so they have 23 chromosomes.

Let each variety self-fertilize for several generation

Co-dominant traits

All tall plants; When two small genes plant ‘tt’ breeds with two tall genes plant ‘TT’ they result in four combinations of all ‘Tt’ genes, where T is dominant and it suppresses the recessive gene t ; so al plants will be tall .

I^AI^A and I^BI^O. I^AI^A will express Blood Type A. I^BI^O will either express blood type B or O. Since O are always recessive then the resulting combinations from where they are inherited are blood type AB or blood type O.

14

Palisade cells are somatic cells and gamete cell contain half the number of chromosome has in its somatic cells. So 28/2=14.

Allowing flowers a parent plant to be self-pollinated.

Self-pollination of F1 progeny will lead to F2 progeny as it happens in monohybrid and Dihybrid crosses.

5643; When Round ‘RR’ and wrinkled ‘rr’ seed bearing plants are crossed, all heterozygous round seed bearing plants are obtained in the F1 generation. When the plants of these F1 generations are cross bred, the F2 generation had round and wrinkled seed bearing plant in the ratio 3:1. (total=4)

Hence, (3/4) * 7524= 5643

Phenotype

It is defined as visible characteristics of an individual which occur from the interaction of its genotype with the environment.

Sexual reproduction

Sexual reproduction involves fusion of gametes which results in exchange of genetic material.

Tallness is the dominant trait.

When a cross between tall plant TT and a short plant tt occurs , the resulting offspring are all ‘Tt’ where T is the dominant trait so all plants are tall due to that dominant trait which does not lets the recessive trait i.e. shortness express itself.

One. XX chromosome in female; XY chromosome in male.

1:1

When pure tall plant TT is crossed with pure short plant tt, all ‘Tt’ offspring are obtained in the F1 generation. When selfing of these F1 generation plants is done, the offspring obtained are ‘TT’ ‘Tt’ ‘Tt’ ‘tt’- in the ratio 3:1 (Tall : short), where pure tall plant and pure short plant are in the ratio 1:1(TT and tt).

Copies of the same chromosome

These versions of traits are known as genes which when brought in by the male and female gametes are found on copies of same chromosome so that they do not assort independently and are said to be linked.

(i) and (iii)

Genes are specific sequences of bases that are present on chromosomes found in nucleus of DNA.

Two individuals of a species

Species is the lowest taxanomic category and share common features, thus two individuals of a species share maximum no. of characters (share common gene pool).

Both maternal and paternal DNA

This is because the gametes coming from the mother and father have genes that carry different traits. When these gametes fuse, the traits are mixed and expressed accordingly.

(iii) and (iv) Y chromosome and X chromosome

Males have all 22 pairs of chromosomes paired perfectly. The 23^rd pair of chromosome that is the pair of sex chromosomes are not paired perfectly because in the pair one chromosome is X and the other is Chromosome Y , so they are not paired perfectly.

The presence of Y chromosome in sperm.

If sperm carries a Y chromosome and fertilizes with egg (having an X chromosome) the sex of the child will be male. But if the sperm carries a X chromosome and fertilizes with egg the sex of the child will be female.

Baby Girl

The mother already has X chromosome in the unfertilized egg. When a sperm, carrying X from the father will fertilize the egg, the combination would be XX and thus a baby girl will develop.

For every type of fat there is a gene

For every hormone production, every protein formation and for production of every enzyme, genes exist but no such genes exist for fat. So the statement (d) is incorrect. Fat is a kind of Acquired characteristic.

Dihybrid cross

Ratio in F2 generation of a Dihybrid cross is always 9:3:3:1

(a)Bb-Brown eyes.(B is dominant which gives brown eyes)

(b)bb-Blue eyes.(b is recessive which gives blue eyes and none dominant gene present)

(c)BB-Brown eyes.(B is dominant which gives brown eyes)

(i) tall- B plant

(ii) dwarf- A plant.

This is because only tall plants appear in the F1 generation and dwarf plants appear in the F2 generation along with tall plants.

(a) Tall plants

(b) 3:1

(c) Dwarf plants.

(a) Red color (Dominancy means ruling over the other)

(b) R and r (R for Dominant and r for recessive)

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)

(a) No brown offspring are produced because brown color is recessive here and black being dominant rules.

(b)Three black mice and one brown mouse will be obtained in F₂ generation; It is a monohybrid cross(Punett Square)

(a) (i) e blue color gene is recessive; recessive is always represented by small letters.

(ii) E brown color gene is dominant; dominant is always represented by capital letters.

(b) They have brown eye color because dominant gene for brown eye color is present which suppresses the recessive gene for blue eye color and hence brown eye color is expressed

(c) Combination of ee will produce children with blue eyes because for blue eye color to be expressed there should not be gene for brown eye color that is E because if E gene will be present it will dominate the eye color and then brown eye color will be expressed and if there will be no dominant gene i.e. ee then the eye color expressed will be blue.

(d) The combinations EE and Ee will produce children with brown eyes because for brown eyes to be expressed there must be at-least one dominant gene for brown eye color i.e. E be present.

The possible genotype that will be inherited by the children when the mother is group A and the father is group B are I^A I^B, I^A I^O, I^B I^O and I^OI^O. The possible blood group likely to be inherited will be either AB,A,B and O

.

No, the parents are not correct. The father is type A and the Mother is type B; the possible genotypes that are inherited by the baby are I^A I^B, I^A I^O, I^B I^O and I^OI^O. This means that any of the blood type AB, A, B, and O can be inherited by the child. If the child inherits any of the one blood type, which is occurring here in this case that the child is inheriting type O blood group, no error has occurred.

Case 1: Man with blood group A married a woman with blood group B. Blood group for man can be expressed by dominant genotype I^AI^A orI^AI^O and blood group O for woman is expressed by recessive genotype I^OI^O. The daughter will have O blood group type as a result of this I^OI^O inheritance of recessive traits from mother and father.

Case 2: Blood group A in father if has recessive genotype I^AI^A and mother has dominant genotype I^AI^O or I^OI^O. The daughter will have O blood type as a result of inheritance of dominant allele I^O from mother and recessive allele I^A from father.

Blood group A is expressed in both homozygous and heterozygous condition but Blood group O is expressed in recessive condition.

The genetic makeup of the tall parent can be depicted as (C) TtWW. As the question says, Tall Pea plants bearing violet flowers; Tallness is a dominant trait and is always represented by capital letters so ‘T’ and short/dwarfness is represented by small letters so ‘t’ – hence Tt. Violet Flowers is a dominant trait and is represented by capital letters so ‘W’. The progeny had short plants but no white flowers which means that Violet flowers are being passed on. Therefore, the genotype of the tall parent can be depicted as TtWW. There is a dominant gene for tallness which suppresses the recessive gene for height and for all violet flowers were present in tall pea plant.

(a)Round Yellow.

Round yellow- RRYY, wrinkled green-rryy. On crossing these two pea plants we get RrYy combination which has dominant gene R for Round shape and Dominant gene Y for yellow color. Hence A-B types of seed produced as a result of the first cross are Round yellow.

(b) A and B are dominant traits since they are Round (R) and yellow (Y)

(c) Round-green

When RrYy obtained in the first generation is self-pollinated, the new varieties obtained are RY, Ry, rY, ry; where RY- Round yellow, Ry-Round green, rY-Wrinkled yellow, and ry- wrinkled green. Since A-B type of seed is Round and yellow, therefore A-D type of seed is Round and Green.

(d) Wrinkled-yellow

When RrYy obtained in the first generation is self-pollinated, the new varieties obtained are RY, Ry, rY, ry; where RY- Round yellow, Ry-Round green, rY-Wrinkled yellow, and ry- wrinkled green. Since A-B type of seed is Round and yellow, therefore C-B type of seed is wrinkled and yellow.

(e)(i) A-D (Round and green ‘Ry’ will be produced in minimum number)

(ii) A-B (Round and yellow ‘RY’ will be produced in maximum number in F2 generation)

(a) (i) The chromosome B are X chromosomes because if person A is entirely madeup of B chromosomes it means the person is a female an has all X chromosomes.

(ii) The chromosome D is X chromosome again because when B and D combine a female offspring is produced. A female zygote can only be produced when both of the chromosomes in the gamete are ‘X’. Chromosome B is X as already said above; now chromosome D is also X. Thus only then when B and D chromosome i.e. X and X chromosome combine, a female zygote is produced.

(iii) The chromosome E is a Y chromosome because when B and E combine a male zygote is produced. B is a X chromosome as discussed above and when E i.e. Y chromosome combine , a male zygote is produced(XY)

(b) Chromosome B and D are of the same type, i.e. X chromosome.

(c) Chromosome E is smaller in size since it is a Y chromosome.

(d) Chromosome B (X) and chromosome E (Y) are known as Sex Chromosomes

(e) (i) C is male since it has half genes from D and half genes from E.

D is a X chromosome and E is a Y chromosome so when they combine a male zygote is formed.

(ii) A is female since it has all B chromosomes in it i.e. X chromosome which is only possible in female.

(a) The F2 generation obtained had Round yellow: Round green: Wrinkled yellow: Wrinkled green in the ratio 9:3:3:1

(i) Round Green seeds- (3/16)*2160= 405

(ii) Wrinkled Green seeds- (1/16)*2160= 135

(iii) Round yellow seeds- (9/16)*2160= 1215

(iv) Wrinkled yellow seeds- (3/16)*2160= 405

(b) Dihybrid ratio has been used in answering this question because here are two different varieties, that differ in two observed traits i.e. Shape : round and wrinkled; Color: yellow and green.

(a) Round-green (RR-round; dominant, yy-green; recessive)

(b) Wrinkled-yellow (rr-wrinkled; recessive, Yy- since one dominant gene Y Is present- yellow)

(c) Wrinkled-yellow (rr-wrinkled; recessive, YY-yellow, dominant)

(d) Round-yellow (Rr-one gene dominant R is present-round; Yy- since one dominant gene Y is present- yellow)

(e) Round-green(RR-round; dominant, yy-green; recessive)

Evolution is the process of gradual changes in heritable characteristics over long time which leads to the formation of new species. These new species develop from their earlier forms during time.

Charles Robert Darwin gave the theory of evolution in his book ‘Origin of Species’ by means of Natural Selection.

The given statement is False. Human beings are more closely related to modern apes but did not evolve from them too. Human beings just share a common ancestor with modern African apes like gorillas and chimps but did not evolve from them.

A feature that is common to both birds and dinosaurs is presence of feathers on their body which shows that birds and dinosaurs are closely related. Dinosaurs had feathers but they could not fly and birds used feathers to provide insulation to their bodies in harsh weather but later on the feathers became useful for flying.

Flatworm – Planaria has rudimentary eyes as eye spots.

All the three, Broccoli, Kohlrabi and Kale have a common ancestor that is wild cabbage.

Plant parts of Wild cabbage or Brassicaoleracea are modified by artificial selection to produce these varieties of cabbage

Flower buds and stem are modified-Broccoli

Stem is modified- Kohlrabi

Leaves are modified- Kale

It is believed that life originated in sea water, near deep sea hydrothermal vents.

Methane, Ammonia and Hydrogen Sulphide are the three inorganic molecules that helped in origin of life on earth. Stanley Miller and Harold Urey performed experiments that showed that organic compounds could b synthesized by stimulating conditions of the early earth atmosphere

Charles Robert Darwin wrote the book “Origin of Species” in which he gave theories of Evolution.

Organs that are similar in structures are known as homologous organs because they have basic design of bones but they have different functions. Forelimbs of frog are used to prop up the front ends of the body when at rest, forelimbs of bird are used for flying, and forelimbs of man are used for grasping.

Two organisms that are now extinct and studied from their fossils are Dinosaurs and Archaeopteryxlithographica.

Dinosaurs are believed to be ancestors of birds. Archaeopteryx is link between reptiles and birds.

(a) Wing of a bird and wing of a bat are homologous organs. They are homologous with their forelimbs which they inherit from common ancestor.

(b) Wing of an insect and wing of a bird are analogous organs. They perform the same function of uplifting the body in air but their basic structure is totally different.

This is because human beings reproduce. There are no geographical barriers so they interbreed easily and produce viable offspring. It is the result of variations that human beings look different from each other in terms of size, color and looks.

Brassica oleracea (wild cabbage) is modified by artificial selection to produce many varieties of vegetables. 5 of such varieties are- Broccoli, Kohlrabi, Kale, Cabbage and Cauliflower.

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.

(a) Homologous organs; Analogous organs.

(Homologous organs are those which have a similar structure; whereas analogous organs are those which have a similar function).

(b) Stages.

(c) Homo Sapiens

(Modern specie of humans is Homo Sapiens). Homo sapiens evolved between 250,000 and 100,000 years ago in Africa.

(d) Wild cabbage (Brassicaoleracea)

(Flower buds and stem are modified traits to produce Kohlrabi)

(e) Charles Robert Darwin.

(Darwin proposed the theory of evolution in his book “Origin Of species”, by means of Natural Selection.

(i) c – petrified remains of prehistoric life

(Dead remains of animals and plants that petrified under environmental conditions over millions of years)

(ii) b – Survival of the fittest

(Evolution occurs over years by the process of natural selection which is based on survival of the fittest)

(iii) e - Archaeopteryx

(Archaeopteryx is a fossil that had been found and studies revealed that it is a fossil of bird since it had avian features)

(iv) a- a famous evolutionist

Charles Darwin wrote the book “Origin of species”

(v) d- father of genetics

Gregor Mendel is the father of genetics.

Acquired traits are not inherited by the organism genetically but by environmental conditions present around the organism or the environmental conditions in which the organism lives. For example, Beetles will reduce in weight if not given enough food.

Whereas,

Inherited traits are those characteristics that an organism inherits from his/her parents i.e., passed on genetically through DNA. (Change in DNA). For example –Change of beetles in color from red to green.

A trait can be only inherited when it brings a change in genes present in the gametes of an organism. Changes in non-reproductive tissues cannot be passed on to DNA of germ cells. Therefore traits acquired during lifetime of an individual are not inherited by the offspring because they are changes in somatic cells and not in germ cells.

No, the wings of a butterfly and the wings of a bat cannot be considered homologous organs because they don’t have similar basic structure, even if they perform similar functions i.e. flying. The wings of bat are supported by bones whereas the wing of a butterfly has no bones but is supported by membranous folds which are attached with muscles and not bones. Wings of a butterfly and wings of a bat are analogous organs which have similar functions but different origins.

Homologous organs are found in humans and lizards. The forelimbs of humans and lizards have different functions completely but the basic structure of bones is similar, i.e. they have same origin. Another example is forelimbs of frog and forelimbs of humans.

Analogous organs are found in bat and butterfly. The wings of a bat and wings of a butterfly have similar function i.e. flying but they have completely different origin.

Another example is wing of an insect and wing of a bird.

Fossils are the dead remains of plants and animals which undergo several physical and chemical processes after they are dead.
Example- Archaeopteryx lithographica is a fossil that resembles a bird(has feathers and wings) but has several features of reptiles(tail and teeth) . So Archaeopteryx is supposed to be the connecting link between aves and reptiles thus suggesting that birds have evolved from reptiles.

If different organisms have common ancestors then it is possible that they have similar characteristics due to inheritance. These similarities are used to determine their close relations in evolutionary terms. For example – forelimbs of bird and forelimb of humans have similar basic structure of bones which suggests that they have a common ancestor i.e. they are closely related in evolutionary terms. Over time these structures have developed to function as per the requirement. Thus homologous organs help in determining closeness in evolution.

Homologous organs are the organs that have different functions but they are believed to have originated from a common ancestor because of their basic structure of bones. Thus if homologous organs are present in different organisms, it can be inferred that they have same ancestors which provide evidences for evolution.

Example- forelimbs of humans and forelimbs of frog; they have different functions but they have same basic design which tells that they have a common ancestor.

Small numbers of surviving tigers are a cause of worry from the point of view of genetics because if all the tigers in the world die and become extinct, their genes will be lost forever, they will not come into sight ever again if they become extinct.

No; Asexual reproduction is a reproduction wherein an organism does not require another organism to reproduce i.e. there is no fusion of gametes. There is very little variation over generations. Thus, geographical isolation cannot be a major factor in the speciation of an organism that reproduces asexually since variations in DNA are not enough to raise a new species.

•Carbon dating is determination of age by studying relative proportion of carbon isotopes.

•Excavating,-Digging the earth.

•Determining DNA sequences and fossil studies

These are some of the techniques that are being used to study evolution.

Bacteria has a better body design in evolutionary terms because they can survive hot springs, deep sea and even freezing environment which most of the other organisms cannot.

Large Variations occur when organisms reproduce sexually. Variations refer to changes in the genetic material of a population. Those which are useful for the population and help in survival are selected by process of natural selection. The accumulation of these variations over time leads to the development of new species. Asexual reproduction brings about very less variation and hence it causes no evolution.

For example- animals that reproduce sexually like birds. If birds with long beaks and few birds with short beaks inhabit a new area which has food that can be eaten only with short beaks. Birds with short beaks will have greater survival chances in such an area and hence they will reproduce more, thus increasing their number and evolving.

(A) A species refers to a group of organisms consisting of similar individuals capable of exchanging genes (interbreeding)

Example

•Plant species- Wheat, Daisies, Conifers, etc.

•Animal species- Cow, Dog, Elephant, etc.

(B) Various factors that could lead to formation of new species are Geographical barrier, natural selection and genetic drift.

•Geographical barrier- if sexually reproducing organisms are isolated by geographical barriers then the gene flow through gametes stops and the isolated members interbreed thus leading to the formation of new species.

•Natural Selection- Nature selects individuals that are better adapted to the environment. The organisms that are better adapted survive and reproduce more, whereas the organisms that are not adapted well to the environmental conditions are slowly erased from the environment.

•Genetic drift- genetic drift is changes in the relative frequency of particular genes which leads to disappearance of those genes as individuals either die or they do not reproduce.

The evidence for the origin of life from lifeless matter was given by Stanley Miller and Harold Urey in 1953. They recreated the probable conditions of primitive atmosphere of early earth and demonstrated that simple organic compound like amino acids, hydroxyl acids, sugars and urea can by synthesized in the laboratory from a mixture of methane, hydrogen, water vapour and ammonia. They supplied energy by heating the chamber containing the above mixture to 800 degree C and discharges by electric sparks. After about one week, the liquid was found to contain a number of amino acids such as glycine, alanine and aspartic acid.

Geographical isolation of a species will lead to the formation of a new species if the species reproduces sexually because isolation will stop the gene flow between the isolated populations since they will not be able to reproduce. As a result, the members of isolated populations will interbreed, leading to the formation of new species.

On the other hand if species that reproduce asexually are geographically isolated, there will be no formation of a new species because such species do not need fusion of gametes to reproduce, they reproduce on their own. Hence there will be no formation of a new species.

Since bacteria have a simpler body plan when compared with human being it does not mean that human beings are more evolved. Bacteria do have a simpler body plan but they have ability to survive harsh environmental conditions/ unfavorable habitats such as high temperature, deep sea hydrothermal vents and freezing temperatures as well. Human beings are also well adapted to the environment they live in. Both, bacteria and human beings have evolved differently

(A) The theory of origin of life on earth was given by J.B.S Haldane.

The theory states that life developed from simple inorganic molecules (methane, ammonia hydrogen sulphide). Haldane said that the conditions on earth at that time including lightning converted these simple inorganic mol.to complex organic molecules that joined together to form the first primitive life forms.

(B) Those species that are now extinct are studied by excavating (digging the earth) and studying their fossils.

Any change in the heritable characteristics of biological population over successive generation is known as Evolution.

Darwin’s theory of evolution – Natural Selection

Variation occurs within a population. Although Species produce a great number of offspring yet the population number remains the same. This constancy in the population number is because of the struggle for resources like food, shelter etc. This Is known as struggle for existence. It favors the fit individuals which survive and reproduce and eliminates the unfavorable ones. This is Natural Selection. These variations accumulate together and they form a new species over time

(A) Analogous organs are organs that are similar in function but have different basic structure which means that they have different origin. For example- Wings of a bird and wings of a bat are analogous organs which have same function of flying but have different basic structure of wings.

Homologous organs are organs that have different functions but have similar basic structure i.e. they have common origin. For example- Forelimbs of man and Forelimbs of frog are similar in structure but they perform completely different functions. Forelimbs of frog are used to prop up at front ends while at rest whereas forelimbs of human are used for grasping.

(B) Analogous organs have similar functions but different origins. Presence of analogous organisms in individuals provides evidence for convergent evolution wherein different organisms with different origins evolve to perform similar functions to adapt to similar environmental niches.

(A) Speciation is the formation of new and different species from existing species in the course of evolution. Speciation occurs when a population gets separated geographically.

(B) No, geographical isolation will not be a major factor in the speciation of a self-pollinating species because self-pollinating plants do not require any other plant to reproduce. Hence, No new gene variants will be introduced into the population and thus there will be no evolution of new species.

(A) Natural Selection – This theory was given by evolutionist Charles Robert Darwin

Natural selection is a process by which organisms that are better adapted to the environment with their characteristics- survive, reproduce and pass their characteristics to their offspring and organisms that are not adapted well to the environment do not survive much due to the requirements that they fail to accomplish and hence their characteristics are not passed on.

(B) Yes; only variations that confer advantage to an individual organism will survive in a population.

For example- In a population of red beetles, some sudden variation in reproduction produces a green colored beetle. Red beetles are a easy source of prey as they can be easily spotted on the green bushes. The green colored beetle that was produced by a variation could mix up with the green bushes and protect itself from being a prey to predator. If the variation that has occurred in the color of the beetle was blue, then it would have been of no advantage to help in surviving, as it would be easily open to predation like the red beetles.

A Chimpanzee is more common in evolutionary terms. Since it’s a African ape and human beings and modern African apes have had common ancestors, chimpanzee is more common in evolutionary terms.

Africa

This is because studies show that human and Modern African Ape shared a common ancestor millions of years ago. So, humans are believed to have evolved in Africa.

Oxygen

Due to the absence of free oxygen, the organic molecules remain unspoiled and reacted to produce new and more complex organic compounds.

Evolution

Evolution is a phenomenon that brings about continuous and orderly changes in nature. It is a change through time in physical or biological world.

The sea

It is believed that life originated about 3.5bya in sea, near deep sea hydrothermal vents.

Reptiles

Aves have evolved from reptiles. Archaeopteryxlithographica is a connecting link between reptiles and aves. The fossil bird was of the size of crow and had both reptilian and avian characters.

Darwin

Charles Robert Darwin wrote a book ‘Origin of Species’ in which he gave The theory of Evolution of species by Natural Selection.

Mendel

Gregor Johann Mendel is known as the father of genetics. He worked on Pea plant and discovered the fundamental laws of inheritance.

Size of body

Size of body cannot be inherited because it depends on division capability of somatic cells and physical efforts also. The rest are inherited through gametes.

Snub nose

This is because the rest of them cannot be inherited as they are related to somatic cell characteristics and learning. Only snub nose can be inherited as its trait would be carried in the gene.

Homologous organs

These organs are similar in their basic structure but they perform different functions. For example- Forelimbs of bird are used for flying, whereas forelimbs of man are used for grasping (i.e. they have same basic structure of bones but perform different functions.)

Analogous organs

These organs perform similar functions but have different basic structure. For example- Wing of an insect and wing of a bird perform the same function of uplifting the body in air but their basic structure is totally different.

Analogous organs

Wing of an insect and forelimb of a bird help them to lift their body up in the air but their basic structure is totally different, so they are analogous organs.

The extinction of organism has occurred thousands of years ago.

Fossils are formed in sedimentary rock which is formed in layers by the deposition and pressure of sediments on top of each other thus the oldest layers are on the bottom, and the youngest layers are on the top.

All variations in a species have equal chances of survival.

This is incorrect because nature follows survival of the fittest. If variation in a species does not let the organism adapt to surroundings it would not survive for long whereas the species that will be able to adapt to surroundings will survive.

Scarred chin

This trait cannot be passed from parents to future offspring because chin gets scarred when the somatic cells of the chin are damaged and it is not a trait that is transferred genetically.

Birds have evolved from reptiles

Reptiles had feathers but could not fly. Over time evolution kept on taking place and with evolution the body size changed and feathers got the ability to help in to flying. Reptiles kept on evolving and their evolution led to the formation of birds which could use feathers for flying. Thus birds have evolved from Reptiles.

Reduction in the weight of an organism due to starvation is genetically controlled.

This statement is incorrect/false. Reduction in weight due to starvation is a result of less amount of food consumed and is not genetically controlled.

New species may be formed if DNA undergoes significant changes in germ cells and Chromosome number changes in the gamete.

If DNA undergoes changes in germ cells that will cause mutations and if chromosome number changes in the gamete it will lead to lethal consequences; both of these changes will lead to formation of new species.

Accumulation of variations over several generations

Variations when accumulate will lead to natural selection and natural selection is based on survival of the fittest. So, a new species is formed when nature starts selecting species that can survive well.

Analogous organs

These organs have different origins i.e. they are not derived from common ancestor, but they perform similar functions. For example- Wings of insect and bat.

Homologous organs

Homologous organs have different functions but they have basic structure of bones which means they have the same ancestor. For example-forelimbs of frog and forelimbs of man. Both have a similar basic structure of bones but forelimbs or frog are used to prop up at front ends when at rest, whereas forelimbs of man are used for grasping.

Spinach

Kohlrabi, cabbage and kale have been produced from Wild cabbage (Brassicaoleracea) by the process of artificial selection.

An arthropod

Trilobite is a fossil group of marine arthropods.

Wings in butterfly and bat

Wings in butterfly and bat are analogous. They have similar functions i.e. flying but they have different ancestors from which they evolved so the pair is not homologous.

Analogous organs

Wings of a housefly and wings of a sparrow are analogous organs since they have similar function which is flying but they have evolved independently in each lineage separately after diverging from an ancestor without wing.