12th Class Biology Chapter 10 Evolution Short Questions Answer

The first  photosythetic  organisms used hydrogen sulphide as a source  of hydrogen for reducing carbon dioxide to sugars.

The eukaryotic cell might have evolved when a large anaerobic(living without oxygen) amoeboid prokaryote ingested small aerobic (living without oxygen) bacteria and stabilized them instead of digesting them.This idea is known as the endosymbiont hypothesis.

The second idea Lamarck adopted was called the inheritance of acquired characteristics.In this concept of heredity the modifications an organism acquires during its lifetime can be passed along to its offspring e.g.the long neck of the giraffe.

The Origin fo Species convinced most biologists that species are products of evolution.An important turning point for evolutionary theory was the birth of population genetics,whixh emphasizes the extensive genetix variation within populations and recongnizes the importance genetic variation within popualtions and recongnizes the importance of quantitative characters.

Natural selection occurs through an interaction between the envionment and the variability ingerent in any population.

It states that the frequencies of alleles and genotypes in a population’s gene pool remain constant over the generations unless acted upon by agents other than sexual recombination.

Individuals with certain genotypes sometimes mate with one another more commonly than would be expected on a random basis.This is called non-random mating.

Darwin’s theory of evolution was mainly based on evidence from the geographical distribution of species and from the fossil record.

Jean Baptiste Lamarck (1744-1829).

A helical bacterium which is flexible and has periplasmic flagella is called sprochete.

The study of geographical distribution of life on earth.Biogeographers attempt to explain the factors that influence where species of plants and animals live on earth.

Any remains impressions or traces of organisms of a formal geological age.

Study of animal development from fertilized egg to formation of all major organs.

The study of biochemical structures and function of organisms at molecular level.

Evolution refers to the processes that have transformed life on earth from its earliest forms to the vast diversity that is observed today.

According to the theory of special creation all living things came into existence in their present forms especially and specifically created by Nature.Among the scientists who believed in divine creation was Carolus Linnaeus.

The idea that organisms might evolve through time with one type fo organism giving rise to another type of organism is called evolution.

Lamarck argued that those parts of the body used extensively to cope with the environment become larger and stronger while those that are not used deteriorate.

Among the birds Darwin collected 13 types of finches that although quite similar seemed to be different species.Some were unique to individual islands while other species were other species were distributed on two or more islands that were close together.

A new species would arise from an ancestral form by the gradual accumulation for adaptations to different environment,separated from original habitat by geographical barriers.Over many generations the two populations could become dissimilar enough to be designated separate species.

Alfred Wallace developed a theory of natural selection essentially identical to Darwin’s.Wallace’s paper along with extracts from Darwin’s unpublished 1844 essay were presented to the Linnaean Society of London on july 1,1858.

Nature will select the organisms whose inherited characteristics fit them best to their environment and eliminate others.

According the neodarwinism the new species evolve due to extensive genetic variation within populations and natural selection.

Evidence from biochemistry molecular biology and cell biology places prokaaryotes as the ancestors of all lofe and predicts that bacteria should precede all eukaryotic life in the fossil record.

Vestigial organs are historical remnants of structures that had important functions in ancestors but are no longer essential.For instance vermiform appendix in carnivores and man.

Ear muscles nictitating membrane vermiform appendix and coccyx in man are vestigial structures.

Homologous organs are functionally different but structurally alike e.g.forelimbs of man bat horse whale etc.are example of divergent evolution.Analogous organs are functionally alike but structurally different e.g.wings of bat birds and insects are examples of convergent evolution.

Natural selection occuurs through an interaction between the environment and the variability ingerent in any population while the selective breeding of domesticated plants and animals by man is artificial selection.

Population is a group of inter-breeding individuals belonging to a particular species and sharing a common geographic area or a population is a localized group of individuals belonging to the same species.

A species is a group of indiduals that have the potential to interbreed in nature.

The total aggregate of genes in a population at any one time is called the population’s gene pool.It consists of all alleles at all gene loci in all individuals of the population.

It stats that the frequencies of alleles and genotypes in a population’s gene pool remain constant over the generations unless acted upon by agents other than sexual recombination.

A general formula called the Hardy-Weinberg equation is used for calculating the frequencies of alleles and genotypes in populations at equilibrium.

1)Mutation 2) Migration 3) Denetic drift 4) Non-random mating 5) Selection

A species which is in imminent danger of extinction throughout its range is called endangered species.A threatened species is likely to become endangered in the near future.

Hydrothermal vents are hot springs deep in the oceans in underwater where life may have begun.

Cheetah,Tiger,Asian,Lion,Indian rhino,Crocodile,Cheer pheasant.

Evoluton is the process by which genetic changes take place in populations of animals and plants over millions of years in response to environmental changes. The believers are termed as ‘evolutionists’.

“Theory of special creation” means that al the living things were created by Nature in their present form and that no changes have occurred in them since they came into existence. The believers of this theory are called as Creationists.

Aristotle was the earliest evolutionist.

Thomas Malthus published the essay on the “Principle of Population”.

Georges Cuvier worked on palaeontology and explained earth’s history by catastrophism.

Charles Lyell published the book “Principles of Geology”.

The underwater hot springs found deep in oceans, from which life might have originated according to one view, are called hydrothermal vents.

The group of bacteria is the archaebacteria (ancient bacteria).

Bacteria were the first photosynthetic organisms. They used carbon dioxide and hydrogen sulphide as raw materials for photosynthesis.

Life was made possible on land 420 million years ago due to the formation of a thick protective layer of ozone in the upper atmosphere.

Prokaryotes originated first, more than 3.5 billion years ago.

The eukaryotes evolved about 1.5 billion years ago.

According to endosymbiont hypothesis, the eukaryotic cell evolved when a large anaerobic amoeboid prokaryote ingested bit not digested small aerobic bacteria which developed into mitochondria. This hypothesis was proposed by Lynn Margulies.

During their evolution, ingestion of prokaryotes that resembled present-day cyanobacteria led to the endosymbiotic development of chloroplasts in plants.

These are the endosymbiont hypothesis and the membrane invagination hypothesis.

Lamarck’s theory regarding evolution was based on use and disuse of organs and the inheritance of acquired characteristics. It was presented in 1809.

Charles Darwin was born in 1809, in Shrewsbury in western England.

Darwin performed voyage on the ship named Beagle, as a Naturalist.

Their name was Galapagos Islands.

Both the theories were quite similar to each other.

Struggle for existence is the competition between various individuals of a population for survival (or in other words for necessities of life).

The survival of organisms better fitted to their environment, in the struggle for existence is called “Natural Selection”.

Lamarck proposed that the species change due to the influence of environment and the use and disuse of organs but Darwin presumed that species change due to natural selection based on hereditary variations.

Population genetics is the study of the number, variety and distribution of genes in a population and of the factors that influence these genes.

The geographical distribution of organisms is known as biogeography.

These are armadillos.

The study and dating of fossils help us to discover the trends in evolution such as which fossil animals (or plants) were the ancestors of what others.

The fossils are either preserved actual remains or parts of organisms that lived in ancient geological times.

Most of the fossils are found in sedimentary rocks.

The change in allele frequency of small population, purely by chance is called genetic drift.