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Since the extent of variations is much larger in sexually reproducing organisms, therefore, the chances of evolution is also much in sexually reproducing These variations enable the organisms to adapt themselves to the changing conditions and also help to face the struggle for Over the time, they and rise to new species. Answer: Genetically organisms are of types. As the chromosomes are the bearer of genes so haploids have single set of genes. A single gene determines the expression of character.
Both the father and mother contribute practically equal amount of genetic material to the child. It means that each trait can be influenced by both paternal and maternal DNA. Answer: No, many of the times the variations are not advantageous to an individual organism but still survive in a population, e.
Most of the other variations not only give survival advantage to an individual but also contribute to genetic drift. Thus, we can say that most of the variations lead to better adaptation of an organism to the changing environment. In this way, it gives survival advantage to that organism and will also survive in the coming population. The science, which deals with study of heredity and variations is called a phylogeny b embryology c genetics d palaeontology Answer: c The genetics is the study of heredity and variations and includes their occurrence, causes, benefits, disadvantages, significance, etc.
Archaeopteryx is a connecting link between a reptiles and aquatic animals b birds and insects c reptiles and birds d birds and dinosaurs Answer: c Archaeopteryx is a connecting link- between the reptiles and birds. It appears like a bird, but has other features which are present in reptiles, e. For palaeontological studies a scientist will gather the evidences from a study of homology b study of analogy c fossils d All of these Answer: d Study of homologous and analogous organs indicates the origin and modification in organisms and study of fossils indicates the age and features of an organism.
In evolutionary terms, we have more in common with [NCERT] a a Chinese school boy b a chimpanzee c a spider d a bacterium Answer: a Chinese school boy because both of us belong to the same species, i. Homo sapiens. Aditya was observing some organisms in lab and tried to compare them. The presence of which organs will confirm to him that they share evolutionary history?
However, these organs perform different functions in different organisms. New species may be formed if I. DNA undergoes significant changes in germ cells. This leads to new variations.
Which of the following statements is not true with respect to variation? Answer: a All variations in a species do not have equal chances of survival.
Some of the variations may be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits.
Such, a newborn cell dies soon. Select the statement that describes characteristics of genes. Answer: b Genes are stretches of DNA found on chromosomes of a cell. A gene contains information for making proteins in a cell. A specific gene is located on a particular chromosome in individuals of a given species. If a round, green seeded pea plant RRyy is crossed with wrinkled, yellow seeded pea plant rrYY , the seeds produced in F1 � generation will be [NCERT Exemplar] a round and yellow b round and green c wrinkled and green d wrinkled and yellow Answer: a The cross between RRyy and rrYY seeds will produce RrYy round and yellow seeds in F1-generation, because round and yellow are the dominant traits.
From the list given below, select the character, which can be acquired but not inherited. The size of the body is an acquired trait because it can vary based on the availability of less or more food. The other three colour of eye and skin and nature of hair are characters inherited from the parents. According to the evolutionary theory, formation of a new species is generally due to [NCERT Exemplar] a sudden creation by nature. Genetic drift accumulates different changes in sub-populations of a species.
Also, natural selection may also operate differendy in the different geographic locations. Eventually, different groups of new species will be formed. Select the incorrect statement. Answer: b The weight reduction due to starvation will not change the DNA of the germ cells, because low weight is not a trait that is genetically controlled or inherited.
Also, low weight parents may have heavy weight progeny. In human males all the chromosomes are paired perfectly except one. Here, one is a normal-sized X-chromosome while other is a short Y-chromosome. Women have a perfect pair of sex chromosomes, both called X.
Rajneesh was studying the fossils of two different types, fossil A was found in upper layer of Earth and B in deeper layers. What can be predicted regarding the age of these fossils? Fossil B found in deeper layer must have become extinct long time ago and deposition of other layers occurred over it during this period.
Heredity Heredity refers to the transmission of characteristics from parent to offspring by means of genes in the chromosomes. Observation: F 1 generation was tall Tt with no halfway characteristics. F 2 generation produced by self pollination of F 1 included tall and short plants in Thus, two copies of the trait are inherited in each sexually reproducing organism.
These two may be identical TT or tt or may be different Tt , depending on the parentage. Conclusion: This study leaded to the formulation of two laws: Law of dominance: states that only one character expresses itself in F, generation. Law of segregation: states that the two alleles of a character in an individual get separated or segregated during gamete formation and distributed randomly in gametes. Experiment 2: He crossed the plant with two different characteristics such as tall plant with round seed and short plant with wrinkled seed.
F 2 generation; tall plants with round seeds, tall with wrinkled seeds, short with round seeds, and short plants with wrinkled seeds in Conclusion: It formulated the law of independent assortment which states that genes of different characters located in different pairs of chromosomes are independent of one another in their segregation during gamete formation.
Evolution And Classification Classification is the process by which organisms are grouped into convenient categories based on some easily observable characters. Characters such as cell type prokaryote or eukaryote , single cell or multi cellular, presence or absence of nucleus, autotrophic such as photosynthesis or heterotrophic, sexual or asexual reproduction etc.
The more characteristics two species will have in common, the more closely they are related. And the more closely they are related, the more recently they will have had a common ancestor. For e. Therefore, classification of species gives a reflection of their evolutionary relationship. Tracing Evolutionary Relationships Few evidences which help us to trace evolutionary relationships among different organisms or species:.
Page Number: Question 1. Answer: Different ways in which individuals with a particular trait may increase in a population are as follow : If it gives the benefit of survival through natural selection. Due to a sudden increase in a particular trait in a population, i. Answer: The factors that would lead to the rise of a new species are the following : Geographical isolation of a population caused by various types of barriers such as mountain ranges, rivers and sea.
The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of pupulation. Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.
Variations caused in individuals due to a natural selection. They tell about the gradual development of complex structured organisms from simple structured organisms. It is known through them that birds are evolved from reptiles. They state that angiosperms are developed from pteriodophytes and gymnosperms. They exhibit the process of humana evolution. In evolutionary terms, we have more in common with : a a Chinese school-boy b a chimpanzee c a spider d a bacterium Answer: a A Chinese school-boy Question 4.
In sexual reproduction variations may occur due to errors in DNA copying. There may be variations due to interchange of homologous chromosomes during crossing over of male and female. In sexual reproduction, it is not predetermined that which gamete would fuse with another gamete. It depends only on chance. It is also a reason of variation.
These variations enable the organisms to adapt themselves to the changing conditions and also help to give rise to new species. Answer: Variations occurring during sexual reproduction may be due to: Separation of homologous chromosomes by chance only during gamete formation. Crossing over recombination of homologous chromosomes. Fertilisation of gametes to form zygote. Errors during DNA copying or mutations. Answer: Genetically organisms are of types i Haploid : They have single set of chromosomes, where each chromosome is represented singly.
When this generation reproduces, the offspring would have differences they inherit from previous generation as well as newly created differences.
Accumulation of these differences generation after generation leads to the development of variations in a population. Different variations provide different advantages to the population and the variation which provide best survival advantages are inherited to the next generation.
Sex Determination Different species use different strategies for this: Environment: for e. It is observed in animals like crocodile, turtle etc. Snails can change sex. Sex of an individual is genetically determined for e. Evolution gives rise to such a biodiversity at each level of biological organization such as at species level, among individuals, molecules etc. Homologous: Similar structure different functions.
It indicates common ancestry for e. Analogous: Similar functions but different structure. Fossils: Remains of hard parts of life-forms found in rocks. Yet, the forelimbs of frogs are adapted to a jumping movement, those of birds are used for flying and those of humans are used for handling tools. This shows that frogs, birds and humans have evolved from a common ancestor. Analogous Organs: Organs which have different design but serve a common function in different animals are called analogous organs.
Wings of birds and wings of bat are good examples of a pair of analogous organs. Wings of birds are composed of all the bones of forelimb and are covered with feathers. Wings of bats are mainly composed of the digital bones and a thin membrane covering the structure.
Yet wings in both the organisms are used for flying. A Mendelian experiment consisted of breeding tall pea plant bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short.
This suggests that the genetic makeup of the tall parent can be depicted as? A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes.
On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not? Answer: This information is not sufficient. For considering a trait as dominant or recessive, we need data of at least three generations. This data is about only two generations. Answer: The modern system of classification is also called phylogenetic classification; which means it is based on evolutionary relationships.
Chapter 6 - Life Processes. Chapter 7 - Control and Coordination. Chapter 8 - How do Organisms Reproduce? Chapter 9 - Heredity and Evolution. Chapter 10 - Light Reflection and Refraction. Chapter 11 - Human Eye and Colourful World. Chapter 12 - Electricity. Chapter 13 - Magnetic Effects of Electric Current. Chapter 14 - Sources of Energy. Chapter 15 - Our Environment. Chapter 16 - Management of Natural Resources.
Variations in organisms happen during reproduction, irrespective of sexual or asexual reproduction.
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