Evolution flash cards

1. 1.What is the Big Bang theory in the context of the origin of the universe?

   It states that the universe originated from a singular huge explosion about 20 billion years ago; the universe expanded and cooled, atoms formed, and eventually galaxies formed.

   Hint: Single explosion, ~20 billion years ago.

2. 2.Approximately when did the Earth form and life first appear?

   Earth formed about 4.5 billion years ago; the first cellular forms of life appeared about 2000 million (2 billion) years ago (first non-cellular life ~3 billion years ago).

   Hint: Earth ~4.5 bya; life much later.

3. 3.What was the theory of Panspermia?

   An early idea that units of life called spores (or 'seeds of life') were transferred to different planets including Earth from outer space.

   Hint: Spores from space; favoured by some astronomers.

4. 4.What is the theory of Spontaneous Generation (Abiogenesis, old view)?

   The idea that life originated from non-living/decaying and rotting matter such as straw and mud spontaneously.

   Hint: Life from dead/decaying matter.

5. 5.How did Louis Pasteur disprove spontaneous generation?

   Using swan-necked flasks, he showed that in pre-sterilised killed yeast flasks no new life arose, while in open flasks new living organisms arose from air; life comes only from pre-existing life.

   Hint: Swan-necked flask experiment.

6. 6.State the Oparin-Haldane theory of the origin of life (chemical evolution).

   Life arose by chemical evolution: the first form of life came from pre-existing non-living organic molecules (RNA, protein etc.) formed from inorganic molecules under conditions of high temperature, volcanic storms, and a reducing atmosphere lacking free oxygen.

   Hint: Chemical evolution; reducing atmosphere; no free O2.

7. 7.What gases made up the early reducing atmosphere proposed by Oparin and Haldane?

   Methane ($CH_4$), ammonia ($NH_3$), hydrogen ($H_2$) and water vapour ($H_2O$); free oxygen was absent.

   Hint: CH4, NH3, H2, water vapour.

8. 8.Describe the Miller-Urey experiment (1953).

   S.L. Miller created conditions similar to primitive atmosphere in a closed flask: $CH_4$, $NH_3$, $H_2$ and water vapour at 800°C with electric discharge (spark). After a week amino acids were formed, supporting chemical evolution.

   Hint: Electric spark over CH4/NH3/H2/water vapour.

9. 9.What did the Miller-Urey experiment demonstrate?

   That simple organic molecules such as amino acids could be synthesised abiotically under conditions simulating the primitive Earth, supporting the Oparin-Haldane hypothesis.

   Hint: Abiotic synthesis of amino acids.

10. 10.What is believed to be the first genetic material and first self-replicating molecule?

    RNA is believed to be the first genetic material and the first self-replicating molecule (the 'RNA world'); later DNA took over as the more stable genetic material.

    Hint: RNA world hypothesis.

11. 11.What is meant by 'chemical evolution' followed by 'biological evolution'?

    Chemical evolution = formation of complex organic molecules from simpler inorganic ones; biological evolution = origin of the first cells and their subsequent evolution into diverse life forms.

    Hint: Molecules first, then cells.

12. 12.What is organic/biological evolution?

    The gradual change in populations of organisms over successive generations, giving rise to new species from pre-existing ones through descent with modification.

    Hint: Descent with modification over generations.

13. 13.Define 'evidences of evolution'.

    Observations from different fields (palaeontology, comparative anatomy, embryology, molecular biology etc.) that provide proof that organisms have evolved from common ancestors.

    Hint: Proofs from many branches of biology.

14. 14.What are fossils and how do they serve as evidence for evolution?

    Fossils are remains or impressions of past organisms preserved in sedimentary rocks; different-aged rock sediments contain fossils of life forms that existed then, showing life forms have changed over time.

    Hint: Palaeontological evidence in rock sediments.

15. 15.How is the age of a fossil estimated?

    By radioactive dating, e.g. carbon dating and other radioisotope methods, based on the layer (strata) of rock in which the fossil is found.

    Hint: Radioactive/carbon dating; rock strata.

16. 16.Which fossil is considered a connecting link between reptiles and birds?

    Archaeopteryx — it had features of both reptiles (teeth, tail, clawed digits) and birds (feathers, wings).

    Hint: Reptile teeth + bird feathers.

17. 17.What are homologous organs? Give the type of evolution they indicate.

    Organs with the same fundamental structure and origin but different functions; they indicate divergent evolution (common ancestry).

    Hint: Same origin, different function → divergent.

18. 18.Give examples of homologous organs.

    Forelimbs of whales, bats, cheetah and humans (same bone arrangement: humerus, radius, ulna, carpals etc.) performing different functions; also vertebrate hearts/brains, and thorns & tendrils of Bougainvillea and Cucurbita.

    Hint: Vertebrate forelimbs; Bougainvillea/Cucurbita.

19. 19.What are analogous organs? What type of evolution do they show?

    Organs with different structure/origin but performing similar functions; they indicate convergent evolution.

    Hint: Different origin, same function → convergent.

20. 20.Give examples of analogous organs.

    Wings of butterfly and birds; eyes of octopus and mammals; flippers of penguins and dolphins; sweet potato (root modification) and potato (stem modification).

    Hint: Butterfly vs bird wing; octopus vs mammal eye.

21. 21.Distinguish divergent from convergent evolution.

    Divergent evolution: same structure develops along different directions due to different needs (homologous organs). Convergent evolution: different structures evolve for the same function (analogous organs).

    Hint: Divergent=homologous; convergent=analogous.

22. 22.What is adaptive radiation? Give a classic example.

    The process of evolution of different species in a given geographical area starting from a point and radiating to other habitats. Example: Darwin's finches of the Galapagos Islands, which evolved varied beak types from a common ancestral seed-eating finch.

    Hint: Darwin's finches; one ancestor → many niches.

23. 23.What is another well-known example of adaptive radiation besides Darwin's finches?

    Australian marsupials — a number of marsupials evolved from a common ancestor within the Australian continent, each adapted to a different habitat.

    Hint: Australian marsupials.

24. 24.What is convergent evolution illustrated by marsupials and placental mammals?

    When more than one adaptive radiation appears to have occurred in an isolated geographical area (e.g. Australian marsupials and placental mammals) producing similar-looking forms, it represents convergent evolution (e.g. placental wolf and Tasmanian wolf-like marsupial).

    Hint: Marsupial vs placental look-alikes.

25. 25.What is embryological evidence for evolution (as originally proposed)?

    Proposed by Ernst Haeckel: vertebrate embryos show similar features during early development (e.g. gill slits/vestigial gill clefts behind the ear) suggesting common ancestry.

    Hint: Haeckel; embryonic gill slits.

26. 26.How did Karl Ernst von Baer's observation modify embryological evidence?

    Von Baer noted that embryos never pass through the adult stages of other animals; Haeckel's proposal that ontogeny recapitulates phylogeny (based on similar embryonic structures) was later criticised/rejected in its strict form.

    Hint: Ontogeny recapitulates phylogeny — later disputed.

27. 27.What is molecular evidence for evolution?

    Similarities in DNA, RNA and proteins (e.g. cytochrome-c, haemoglobin) among diverse organisms indicate common ancestry; the more similar the molecules, the closer the evolutionary relationship.

    Hint: Comparing DNA/proteins across species.

28. 28.What are vestigial organs and how do they support evolution?

    Vestigial organs are reduced, non-functional structures that were functional in ancestors, indicating common descent. In humans: vermiform appendix, nictitating membrane of the eye, ear muscles, coccyx, body hair.

    Hint: Reduced useless organs, e.g. appendix.

29. 29.How does industrial melanism in the peppered moth (Biston betularia) demonstrate natural selection?

    Before industrialisation in England, white-winged (light) moths dominated on lichen-covered trees; after industrialisation, soot darkened tree trunks and dark (melanic) moths survived better (camouflage), increasing in number. It shows natural selection in action.

    Hint: Peppered moth; pollution favours dark morph.

30. 30.How do DDT-resistant mosquitoes / antibiotic-resistant bacteria illustrate evolution?

    When exposed to a pesticide/antibiotic, susceptible individuals die but resistant variants survive and reproduce, so the resistant type increases in frequency — an observable example of evolution by natural selection.

    Hint: Resistance spreading under selection pressure.

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