evolution

Question 1

universe how old?

Answer 1

20 billion

Question 1

how are stellar distances measured?

Answer 1

in light years

Question 2

when earth formed?

Answer 2

4.5 billion yrs ago

Question 3

conditions of early earth

Answer 3

• no atmosphere
• water vapour, carbondioxide, ammonia, methane released from molten mass covered the surface
• UV rays broke up water into Hydrogen and Oxygen and the lighter H2 escaped.
• Oxygen sombined with ammonia and methane to form water, carbondioxide, etc.
• Ozone layer was formed and as it cooled, water vapour fell as rain to fill all the depressions and form oceans.

Question 4

when did life appear

Answer 4

4 billion years ago/500 million years after formation of earth

Question 5

theories on origin of life

Answer 5

1) Panspermia
2) Spontaneous generation
3) chemical evolution
4) biogenesis

Question 6

Panspermia

Answer 6

• scientists believe that it came from outside
• early greek thinkers believed units of life called spores were transferred to different planets, including earth.

Question 7

Spontaneous generation

Answer 7

• LIFE CAME OUT OF DECAYING AND ROTTING MATTER SUCH AS STRAW, MUD, ETC.
• disproved by louis pasteur by experiment: life did not come from killed yeast in pre-sterilized sealed flasks while in another flask open to air, life arose from the “killed yeast”

Question 8

Chemical Evolution and Biogenesis

Answer 8

• Oparin of Russia and Haldane of England proposed the first form of life could have come from pre-existing non-living organic molecules and that formation was preceeded by chemical evolution i.e, formation of diverse organic molecules from inorganic constitutents.
  Biogenesis- life arose slowly through evolutionary forces from non-living molecules

Question 9

Urey and miller experimetn

Answer 9

American scientist, S.L. Miller created similar condtions of early earth (high temperature, volcanic storms, reducing atmosphere containing CH4, NH3, etc)
- He created electric discharge in a closed flask containing methane, ammonia, hydrogen and water vapour at 800 degree C and observed the formation of amino acids.

Question 10

first non cellular forms of life originated when and first cellular forms of life when

Answer 10

• 3mya and 2000 mya

Question 11

theories on evolution

Answer 11

1) special creation
2) lamarck
3) darwinism

Question 12

special creation theory

Answer 12

1) that all living organisms (species or types) that we see today were created as such
2) That the diversity was always the same since creation and will be the same in the future also
3) that the earth is 4,000 years old

Question 13

Lamarck

Answer 13

-French Naturalist Lamarck had said that evolution of life forms had occurred but driven by use and disuse of organs.
-He gave the example of Giraffes who in an attempt to forage leaves on tall trees had to adapt by elongation of their necks. -They passed on this acquired character of elongated neck to succeeding generations.
-Giraffes, slowly over the years, came to acquire long necks.

Question 14

darwinism

Answer 14

1) All the existing life forms share similarities and share common ancestors
2) concluded that existing life forms share similarities to varying degrees not only amongst themselves but also with life forms that existed millions of years ago.
3) Many such life forms do not exist anymore
4) There had been extinctions of different life forms in the yearsd gone by just as new forms of life arose at different periods of history of earth.
4) there has been gradual evolution of life forms
5) any population has built in variations of characteristics and those which enable some to survive better in natural conditions (climate, food, physical factors,etc.) outbreed those who are less endowed to survive under such conditions[fitness of the individual hence, those who are better fit in an environment leave more progeny than others]

Question 15

who else came up with similar conclusions?

Answer 15

Alfred Wallace, a naturalist who worked in Malay Archipelago had also come to similar conclusions around the same time.

Question 16

Adaptive radiation

Answer 16

• The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation.
  eg: darwin;s finches and australian marsupials

Question 17

convergent evolution

Answer 17

when more than one adaptive radiation appeared to have occurred in an isolated geographical area (representing different habitats) it is geographical evolution
- for eg: Placental mammals in australia also exhibit adaptive radiation in evolving into varitiies of such placental mammals each of which appear to be ‘similar’ to a corresponding marsupial (eg: placental wolf, tasmanian wolf).

Question 18

Industrial melanism

Answer 18

1. In a collection of moths made in the 1850’s i.e., before industrialisation set in England, it was observed that there were more white-winged moths than dark ones or melanissed moths.
2. However, in the collection carried out from the same area but after industrialisation, i.e, in 1920, there were more dark-winged moths in the same area that is the proportion was reversed.
3. The explanation put forth for this observation was that ‘predators spot a moth against a contrasting background’.
4. DUring post-industrialisation period, the tree trunks had become dark due to industrial smoke and soots. Under this condition, the white winged moths did not survive due to predators, the dark winged or melanised moths survived.
5. Before indsutrialisation set in, thick growth of almost white-colored lichens [do not grow in areas that are polluted] covered the trees-in that background, the white winged moth survived but the dark-coloured moths were picked out by predators.
6. Hence, moths that were able to camouflage themselves that is ,hide in the background survived.
7. This showed that in a mixed population, those who can better adapt, survived and increased in population size but no variant is completely wiped out.

Question 19

Paleontological evidence

Answer 19

• Fossils are remained of hard parts of life-forms found in rocks.
• Different-aged rock sediments contain fossils of different life-forms who probably died during the formation of the particular sediment.
• They represent the extinct organisms (e.g. Dinosaurs).
• A study of fossils in different sedimentary layers indicates the geological period in which they existed.
• The study showed that life-forms varied over time, from simple to complex, and certain life forms are restricted to certain geological time-span.
• Hence new lives have arisen at different times in the history of earth.

Question 20

4. COMPARATIVE ANATOMY AND MORPHOLOGY(2 types?)

Answer 20

i. Homologous organs and Divergent evolution
ii. Convergent evolution and Analogous organs

Question 21

i. Homologous organs and Divergent evolution