Science Olympiad Test: Heredity and Evolution- 2 - Class 10 MCQ

Males have XY sex chromosomes while females have XX sex chromosomes; the male can contribute the X or Y chromosome, while the female must contribute one of their X chromosomes. A male infant results if the male contributes his Y chromosome while a female infant results if he contributes his X chromosome.

There are 23 pairs of chromosomes i.e 46 chromosomes in a human cell. The sex chromosomes are the chromosomes that determine the sex (male or female) of an organism. There is only one pair of sex chromosome in a human cell which may be XX (for female) or XY (for male). If a sperm carrying chromosome X fertilizes the egg then the sex of the offspring will be female (XX). This is because the chromosome of an egg cell will always be X. 

• The fossils are studied to determine the location and the origin of the organism. 
• The fossils of the ancient human species Homo Naledi were excavated in the southern regions of Africa. 
• With the help of research, the genetic footprint of humans can be traced back to Africa.

Thus, the correct answer is option C. 

Trilobites are an extinct group of arthropods (jointed-legged animals) known from more than 10,000 fossil species. 
The group Trilobita existed from early in the Cambrian Period (520 million years ago) until the end of the Permian Period (250 million years ago). The name Trilobita is derived from the three (tri-) lobed structure of the exoskeleton, which has a raised central lobe (or axis) and a pair of side lobes, called as pleurae. The trilobite body is also divided lengthwise into three regions or tagmata: a head or cephalon, a middle region (thorax) composed of several to many articulated segments, and a tail plate called as a pygidium, which consists of fused segments.

Scarred chin is an acquired trait, which an individual gets due to an accident. It cannot be passed on to the progeny.

Visible characteristics of an organism are called phenotype. The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.

In the case of asexual reproduction, only the minimal changes due to inaccuracies in DNA copying pass on to the progeny. Thus, offspring of asexual reproduction are more or less genetically similar to their parents. So, it can be concluded that evolution in sexually reproducing organisms proceed at a faster pace than in asexually reproducing organisms.

• Sexual reproduction is a mode of reproduction where new organisms are produced by the exchange of genetic material during fertilization. 
• Vegetative propagation and budding are forms of asexual reproduction and there is no exchange of genetic material in asexual reproduction.

All variations in a species have equal chance of survival Obviously not. Depending on the nature of variations, different individuals would have different kinds of advantages.

Spinach has not been produced from wild cabbage by the process of artificial selection.

Sex determination seen in humans is XY sex determination. Ovum carries X chromosome, whereas sperm can carry either X or Y chromosome. The genetic makeup of a female is XX and genetic makeup of male is XY. Therefore, if the zygote is formed by receiving the X chromosome from the father, the resulting zygote will be a female. 

• In a sexually reproducing population, the genes are present in different forms or alleles. 
• The different alleles are present on different copies of the same chromosomes. In a normally diploid sexually reproducing population like humans, each individual has 23 pairs of chromosomes. 
• Thus, there are two copies of each chromosome. 
• One of the chromosomes (of each pair) comes from the father through male gamete and the other chromosome (of each pair) comes from mother through the female gamete. After the process of fertilization, the zygote is produced having 23 pairs of chromosomes, with alleles for a trait present on the homologous pair.

So, the correct answer is 'Copies of the same chromosome'

Frequency of certain genes in a population change over several generations resulting in evolution. The factors affecting change in genetic frequency are natural selection, genetic drift, mutations and gene flow. Weight loss or gain occurs due to external factors such as food and is not genetically controlled. Hence, low weight parents can have heavy weight progeny due to difference in food habit. Frequency of inherited traits change over generation and causes evolution whereas traits that are not inherited over generations like dancing, playing guitar do not cause evolution. 

1. Fossils are clear proof of evolution.
2. Fossils are the bodily remains or imprints of deceased plants and animals that have been preserved in layers of the Earth and rocks.
3. Older fossils are discovered deeper into the Earth.
4. The extinction of organisms is thought to have occurred thousands of years ago.

A baby’s sex is determined at the time of conception. When the baby is conceived, a chromosome from the sperm cell, either X or Y, fuses with the X chromosome in the egg cell, determining whether the baby will be female (XX) or male (XY)To be female, one needs to be (XX), whereas to be a male, (XY) is needed. It is the Y chromosome that is essential for the development of the male reproductive organs, and with no Y chromosome, an embryo will develop into a female.

In terms of evolution, organisms belonging to the same species have more in common than organisms belonging to different species of the same genus or different genus. We have more in common with a Chinese school-boy because both belongs to the same species of Homo sapiens, and thus, share a common ancestor.