Live practice

1. They persist and accumulate in soil and water, causing pollution, blocking drains and physically harming animals that swallow or become trapped in them.
2. Toxic non-biodegradable chemicals may enter food chains. Their concentration can increase at successive trophic levels through biological magnification and may become harmful to top consumers, including humans.

Using the right-hand grip rule, curl fingers clockwise. The thumb points into the table, so the field through the interior is downward/into the table. The closed field lines return outside the loop, where their direction is upward/out of the table.

Potential difference is work done per unit charge, \(V=\frac{W}{Q}\). A value of 1 V means 1 J of work is done in moving 1 C between the points.

Ciliary muscles alter the eye-lens curvature; this ability is accommodation.

Using the Cartesian convention, a convex mirror has positive radius:

The mother with group O has genotype OO. Their group-O daughter must receive O from each parent, so the group-A father must be AO. Because he carries both alleles but expresses group A, A is dominant over O and O is recessive. The evidence is therefore sufficient for this pair of traits.

Their bodies contain highly specialised tissues arranged into organs and organ systems. A random fragment lacks the complete positional information and organisation needed to reconstruct every system. Regeneration is mainly a repair process. Only organisms with simpler organisation and many undifferentiated cells can regenerate whole individuals readily.

The immediate response is coordinated in the spinal cord to save time. At the same time, impulses travel to the brain, making us conscious of the stimulus and pain. The brain can then interpret the event, modify later responses and initiate additional voluntary action. Thus the brain is informed even though it need not start the first withdrawal.

Autotrophs manufacture organic food from inorganic carbon dioxide and water using light energy and chlorophyll; green plants are examples. Heterotrophs obtain ready-made organic food from other organisms and digest it before absorption; animals and fungi are examples. Autotrophs are producers, whereas heterotrophs depend directly or indirectly on producers.

A cycloalkane has general formula \(\ce{C_nH_{2n}}\); for \(n=5\), cyclopentane is \(\ce{C5H10}\). Five \(\ce{CH2}\) groups join in a ring by C-C single bonds. Each carbon bonds to two neighbouring carbons and two hydrogen atoms, completing four bonds.