Biology Today — January 2018

(Jacob Rumans) #1

  1. Two statements regarding evolution are made below.
    I. Rates of evolution are typically very slow because
    natural selection is usually _P selection.
    II. The plant population growing on high-zinc-soil is able
    to grow at concentrations which are otherwise lethal
    to plants of the same species. This is Q
    selection. P and Q refer to
    (a) directional and disruptive selection respectively
    (b) stabilising and directional selection respectively
    (c) directional selection
    (d) stabilising selection. (INBO 2017)

  2. Fish utilise oxygen dissolved in water. When the temperature
    of water rises, it can pose physiological stress to the fish as
    solubility of oxygen in water decreases. Which of the following
    graphs correctly depicts the oxygen consumption rates of
    resting fish and active fish under these conditions?
    Note: Oxygen consumption by active fish is indicated by
    solid line and by resting fish is indicated by dashed line.


(a)

Water temperature

Oxygen consumption

arbitrary units
10°C 40°C

(b)

Oxygen consumption

arbitrary units
10°C 40°C
Water temperature

(c)

Water temperature

Oxygen consumption

arbitrary units
10°C 40°C

(d)

Oxygen consumption

arbitrary units
10°C 40°C
Water temperature
(INBO 2016)


  1. An experiment to understand the relationship between
    a herbivorous crab Mithrax forceps and the coral Oculina
    arbuscula was undertaken in a shallow water coastal
    ecosystem. Observation on predation of crab, growth
    of algae, growth and mortality of corals were made. The
    following graphs indicate the results obtained during the
    experiment.


Predation of M. forceps with or without corals

After 1 hour
Crabs with access to corals Crabs without access to corals

After 24 hours

16

8
6
4
2
0

14
12
10

Number of crabs consumed

Algal growth

No crab Crab

25

15

5

20

10

Algal growth over coral (% of coral mass)^0

Coral growth

No crab Crab

14

8

4
2

12

6

Coral growth (% mass change per month)^0

Coral mortality

No crab Crab

80

20

30

40

50

60

70

10
0

Coral mortality (%)

A few statements based on the results obtained are made.
i. The presence of crabs has a negative influence on algal
growth and positive influence on coral growth.
ii. Presence of M. forceps is obligatory for the survival of
O. arbuscula.
iii. The coral species plays an important role in preventing
predation of M. forceps.
iv. The algae outcompete O. arbuscula in the absence of
M. Forceps.
Which of these statements are true?
(a) i, ii and iii only (b) i and iv only
(c) i, iii and iv only (d) iii and iv only
(INBO 2016)


  1. Animals belonging to the following groups are usually
    hermaphrodites except
    (a) gastropods (b) oligochaetes
    (c) crustaceans (d) flatworms.
    (NSEB 2015-16)

  2. Which of the following individuals will produce 16 types of
    gametes?
    (a) AaBbccDdeeFF (b) AaBbccDDEeFf
    (c) AaBbCcddEEFF (d) AaBbCcDDEeFf
    (NSEB 2015-16)


BIOLOGY


OLYMPIAD PROBLEMS

Free download pdf