NEET · Biology doubts
340 doubts found
Why are so many flowers brightly coloured, scented and full of nectar?
These flowers rely on animals — insects, birds or bats — to carry pollen from one plant to another (cross-pollination).
How does a spoonful of old curd turn a bowl of warm milk into fresh curd?
The starter curd carries Lactobacillus bacteria.
A colour-blind man marries a woman with no colour blindness in her family. Why are their sons normal but their daughters carriers?
Colour blindness is X-linked recessive.
How did the Meselson-Stahl experiment prove DNA replication is semiconservative?
Bacteria were grown in heavy nitrogen (15N) so all their DNA was dense, then shifted to light 14N.
A bird's wing and a butterfly's wing do the same job, so why are they NOT evidence of common ancestry?
They are analogous, not homologous.
An Rh-negative mother's first Rh-positive baby is usually safe, but a second one is at risk. Why?
During the first delivery some Rh-positive fetal blood leaks into the Rh-negative mother, and she begins making anti-Rh antibodies -- but too late to harm the first baby.
When you touch a hot object your hand jerks back before you feel the pain. How?
This is a spinal reflex.
Why are natural food chains usually limited to just four or five trophic levels?
Energy transfer between trophic levels is very inefficient -- only about 10% of the energy at one level is captured by the next, the rest lost as heat and respiration.
Why do scientists prefer restriction enzymes that leave 'sticky ends' when making recombinant DNA?
Many restriction enzymes cut the two DNA strands in a staggered way, leaving short single-stranded overhangs called sticky ends.
A snakebite victim is given antivenom, not a vaccine. Why?
A vaccine works by getting the body to make its own antibodies and memory cells, which takes days to weeks.
I keep getting “Cell theory” questions wrong in Cell: The Unit of Life. What's the trap?
forgetting Virchow's addition that cells come only from other cells.
I keep getting “Enzymes” questions wrong in Biomolecules. What's the trap?
thinking enzymes are used up in the reaction.
I keep getting “Phases of the cell cycle” questions wrong in Cell Cycle & Cell Division. What's the trap?
thinking DNA is copied during mitosis.
I keep getting “Light reactions” questions wrong in Photosynthesis in Higher Plants. What's the trap?
thinking the released oxygen comes from carbon dioxide.
I keep getting “Glycolysis” questions wrong in Respiration in Plants. What's the trap?
thinking glycolysis needs oxygen.
I keep getting “Digestive enzymes” questions wrong in Digestion & Absorption. What's the trap?
thinking pepsin works in the mouth.
I keep getting “Gas exchange” questions wrong in Breathing & Exchange of Gases. What's the trap?
thinking gases are actively pumped across the alveoli.
I keep getting “Double circulation” questions wrong in Body Fluids & Circulation. What's the trap?
thinking humans have single circulation like fish.
I keep getting “Nephron” questions wrong in Excretory Products & Elimination. What's the trap?
thinking the whole kidney filters as one unit.
I keep getting “Neuron” questions wrong in Neural Control & Coordination. What's the trap?
thinking the axon receives signals.
I keep getting “Hormones” questions wrong in Chemical Coordination (Endocrine System). What's the trap?
confusing endocrine glands with exocrine glands that use ducts.
I keep getting “Mendel's laws” questions wrong in Principles of Inheritance & Variation. What's the trap?
thinking both alleles blend rather than segregate.
I keep getting “DNA structure” questions wrong in Molecular Basis of Inheritance. What's the trap?
pairing adenine with guanine or cytosine.
I keep getting “Natural selection” questions wrong in Evolution. What's the trap?
reading it as 'survival of the strongest'.