BIOLOGY 3 Marks Question

→ In 1953, an American scientist named S. L. Miller created in the laboratory a condition similar to the Earth's primordial atmosphere.
→ He mixed CH₄, H₂, NH₃ and water vapour in a closed flask at a temperature of 800°C and arranged the electrodes and gave electric shocks. Then the mixture was cooled in the condenser and made a liquid.
→ He Collected the liquid in a separate flask.
→ After two weeks of the procedure, the fluid was analyzed by chromatography.
→ He found that amino acids were formed in it. Besides hydroxy acids (scientific name of H₂O) and aliphatic acids were also present.
→ Similarly, other scientists have observed in this type of experiment that sugars, nitrogen bases, pigments and fats were produced.

→ In a given population one can find out the frequency of occurrence of alleles of a gene or a locus.
→ This frequency is supposed to remain fixed and even remain the same through generations.
→ Hardy-Weinberg principle stated it using algebraic equations.
→ This principle says that allele frequencies in a population are stable and is constant from generation to generation.
→ The gene pool (total genes and their alleles in a population) remains a constant. This is called genetic equilibrium.
→ Sum total of all the allelic frequencies is 1. Individual frequencies, for example, can be named p, q etc.
→ In a diploid, p and q represent the frequency of allele A and allele a.
→ p² + 2pq + q² =1. This is a binomial
expansion of (p + q)².Where : p² - Frequency of individuals with Where: p genotype AA.
q² - Frequency of individuals with genotype aa. 2pq - Frequency of individuals with genotype Aa.
→ When frequency measured, differs from expected values, the difference (direction). indicates the extent of evolutionary change.
→ Disturbance in genetic equilibrium, or Hardy-Weinberg equilibrium, i.e. change of frequency of alleles in a population would then be interpreted as resulting in evolution.

→ The process of development of different species starting from one point of a given geographical area to other geographical habitats is called adaptive radiation.
Darwin finch
→ Darwin Finch is an excellent example of this type of phenomenon.
→ Darwin saw several species of finches across the Galapagos Islands.
→ He speculated that all species had evolved on the island by themselves.
→ Along with other features of the original finches (seed eating), their beaks may have evolved for other forms that made them insectivorous and herbivorous finches.
Australian marsupials
→ Another example is the Australian marsupial.
→ Most marsupials were different from each other.
They evolved from a common set of ancestors, but they all evolved on the Australian island continent.
→ When more than one adaptive diffusion occurs in a geographical area (representing different habitats) it is called convergent evolution.
→ Mammals of Australia marsupials (E.g.:- the wolf and the Tasmanian wolf) show a similar evolution.

Placental mammals	Australian Marsupials
Mole	Marsupial mole
Ant eater	Numbat (Ant eater)
Mouse	Marsupial mouse
Lemur	Spotted cuscus
Flying squirrel	Flying phalanger
Bobcat	Tasmanian tiger cat
Wolf	Tasmanian wolf

→ Solution:
→ Human evolution can be based on different components, namely:
• Size of the brain
• Body posture
• Food habits/dietary preferences
• Characteristics/features
→ The following table depicts the same:

Human evolution stages	Size of the brain	Body posture	Food preferences	Features
Dryopithecus africans	-	Knuckle-walking, ape- like walk	Leaves and tender fruits	Equal-sized arms and legs, large canines
Ramapethicus	-	Semi-erect posture	Nuts and seeds	Large molars, small canines
Australopithecus africanus	450 cc	Completely erect posture, around 1.05m tall	Fruits (herbivorous)	Inhabited trees, stone weapons for hunting, incisors & canines are smaller
Homo habilis	735 cc	Completely erect posture, around 1.5m tall	Carnivorous	Small canines, first to make tools
Homo erectus	800 cc to 1100 cc	Completely erect posture, around 1.5m - 1.8m tall	Omnivorous	For hunting, used bone and stone tools
Homo neanderthalensis	1300 cc to 1600 cc	Completely erect posture, around 1.5m - 1.66m tall	Omnivorous	Inhabited caves, buried their deads, hid their bodies for protection
Homo sapiens fossilis	1650 cc	Completely erect posture, 1.8m	Omnivorous	Possessed strong jaw with teeth closely placed, inhabited caves and made carvings and paintings in caves. Developed a culture and were referred to as the first modern men.
Homo sapiens sapiens	1200 cc to 1600 cc	Completely erect posture, around 1.5m - 1.8m tall	Omnivorous	Possess a high intelligence quotient, referred to as the living modern man. Developed language, speech, culture, art and language. Cultivation of crops and domestication of animals observed.

→ Solution:
Fossil discovery of dinosaurs had some interesting revelations.
→ It sheds light on the evolution of reptiles in the Jurrasic era.
→ This revelation gave rise to the discovery of the evolution of other animals, such as mammals and birds.
→ Two unfamiliar fossils recently unearthed in China led to a controversy over the evolution of birds. One such genus of primitive birds were Confuciusornis.
→ These were crow-sized and thrived during the Cretaceous era in China.

→ An interesting observation of melanic Moth supporting the development by natural selection comes from England.
→ In a collection of Moths made in 1850, i.e. before industrialisation. Set in, it was observed that.
→ But after industrialization i.e. in 1920 more dark winged moths were seen in the same area i.e. the proportion was reversed.
→ From this observation, it is suggested that, "Predators find spots in a contrasting background".
→ In the contrasting background under the effect of this condition white-winged moths did not survive due to predators, but dark-winged OR melanised moth plants survived.
→ Before industrialization, the lichen was almost white in color.
→ White-winged plants survived in a background containing white lichens, but dark-winged moths were eaten by predators.

→ Thus the particles that could be colored could make their existence.
→ This explanation is supported by the fact that where there is no industrialization, the number of melanic moth is low.
→ This shows that in mixed populations they adapt better, survive and increase population life.
→ Absence of lichen suggests industrial pollution (which is indicative).

→ Ideas related to the evolution of living form are based on the observations of Charles Darwin during his voyage around the world in the ocean liner H.M.S. Beagle.
→ Charles Darwin concluded that organisms on Earth not only resembled each other, they also resembled organisms from years ago.
→ Many of these organisms are extinct.
→ Some organisms have become extinct in different periods in the history of the earth, against which some new ones have also appeared.
→ Organisms are evolved gradually. Any population is stable due to variation in traits.
→ Characteristics that some natural situations (air, food, physical elements etc.) enables better survival.
→ This situation tends to leave behind less able organisms.
→ Population that have good fitness can survive on the earth (survival of the fittest rule).
→ According to Darwin fitness means only reproductive fitness.
→ Organisms that are better suited to the environment can produce more offspring than others to survive longer and nature selects them, which Darwin called natural selection.

→ The rate of emergence of new forms of organisms and the life cycle OR are related to life span.
→ The rate at which new forms of organisms appear and is related to the life cycle or life span.
→ Rapidly dividing microorganisms have high multiplicity, reach millions within hours.
→ A colony of bacteria growing in a given culture medium (say A) varies in terms of its ability to utilize food components.
→ If the composition of the medium is changed, only that fraction of the population (say B) that survives the changed condition will remain.
→ Over a certain period of time, a variant form of this population will outgrow the others and come into being as a new species.
→ But when this matter is applied to fish or chicken, it takes millions of years because their life span is in years.
→ It can be said that B's fitness is better than A's under the new conditions.
→ So called fitness are based on characteristics or inherited.
→ Therefore there must be a genetic basis for selection and development.
→ In other words some organisms are better adapted to survive in a changing environment.
→ Adaptability is hereditary. It has genetic basis.
→ Fitness is the end result of the ability to adapt and to be selected by nature.
→ Two key evolutionary concepts developed by Darwin are natural selection and branching.
→ Darwin stated that variations that are inherited and are well adapted to a particular habitat and resource.