Questions 40-50
2 N& W1 ~0 k0 |6 J6 D& ?4 x. `Pheromones are substances that serve as chemical signals between members of the
u. O0 |1 N6 K, S+ q& Q* L3 bsame species. They are secreted to the outside of the body and cause other individuals6 v$ |/ @1 F4 W% c" |8 T# M
of the species to have specific reactions. Pheromones, which are sometimes called
4 ?9 x8 U2 n/ J. b5 `Line "social hormones," affect a group of individuals somewhat like hormones do an individual/ x- |! C" r+ d- D8 H3 \
(5) animal. Pheromones are the predominant medium of communication among insects- ~# q/ Q; G! T% N$ b% Q4 \
(but rarely the sole method). Some species have simple pheromone systems and produce
1 ^. U( _* ~/ @$ }only a few pheromones, but others produce many with various functions. Pheromone0 w8 B4 O# m1 C r' C
systems are the most complex in some of the so-called social insects, insects that live
/ L1 R& e- K0 o6 T* N: ein organized groups.
& h/ ?- C% h- f( }7 {(10) Chemical communication differs from that by sight or sound in several ways.* L2 r; q/ d3 N% r1 n2 H( T
Transmission is relatively slow (the chemical signals are usually airborne), but the
+ y* `( b9 q2 _: ^# G- ~signal can be persistent, depending upon the volatility of the chemical, and is sometimes
- I2 u8 Y0 s9 W: @: m4 G6 t7 X' ~effective over a very long range. Localization of the signal is generally poorer than
+ Q0 m; M4 E# H8 o4 U q+ qlocalization of a sound or visual stimulus and is usually effected by the animal's moving0 _" B2 V& f; Y
(15) upwind in response to the stimulus. The ability to modulate a chemical signal is limited,; ]3 G# m f/ n! t8 {9 ?# h
compared with communication by visual or acoustic means, but some pheromones may
' C. |4 n6 {* `* X8 ^1 z. qconvey different meanings and consequently result in different behavioral or physiological6 C! o$ u4 A, K2 j, ~
responses, depending on their concentration or when presented in combination. The
1 L, _: [* s6 }8 T. l5 r. dmodulation of chemical signals occurs via the elaboration of the number of exocrine
5 ~: N- {1 s/ h* D& {% A' k(20) glands that produce pheromones. Some species, such as ants, seem to be very articulate+ U7 e9 T/ m! R2 \
creatures, but their medium of communication is difficult for humans to study and- \2 E& ?+ R7 }- r
appreciate because of our own olfactory, insensitivity and the technological difficulties
. ~! m- g3 i: w) t) Q, Yin detecting and analyzing these pheromones.2 y5 {) C$ `9 s1 b' t
Pheromones play numerous roles in the activities of insects. They may act as alarm" N8 L+ _3 q l. T6 G' p
(25) substances, play a role in individual and group recognition, serve as attractants between
& y/ K |3 H+ R2 q! V+ D4 Q5 ssexes, mediate the formation of aggregations, identify foraging trails, and be involved in
0 k/ R5 r- i4 k4 C% _caste determination. For example, pheromones involved in caste determination include
: g" u# }3 c. Y* G5 U' f3 Vthe "queen substance" produced by queen honey bees. Aphids, which are particularly
! e, D h% z$ L3 Z. u- v1 Hvulnerable to predators because of their gregarious habits and sedentary nature, secrete
6 [2 D) Q3 z" x) E! _. san alarm pheromone when attacked that causes nearby aphids to respond by moving away.
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40. What does the passage mainly discuss?
0 r6 d& G% [2 P# Z% t(A) How insects use pheromones to communicate. I7 C% Z! J$ c* o
(B) How pheromones are produced by insects
@" x7 Y% l+ s. I(C) Why analyzing insect pheromones is difficult5 ], |& ~0 Y! ?9 s
(D) The different uses of pheromones among various insect species
/ f2 @! B- f3 t0 ~41. The word "serve" in line I is closest in meaning to0 s4 P6 y k9 |
(A) improve1 I, |- V* B! r2 C! r( ]% u
(B) function6 y K. A( E ~
(C) begin
+ Q6 H% {& t7 m3 q6 I(D) rely
+ ^# V+ W7 @5 v5 }$ g/ |' {. a% ]' r) b42. The purpose of the second mention of "hormones" in line 4 is to point out
- ?3 T# A4 G4 \" o7 b(A) chemical signals that are common among insects
% D( q; t( g4 T# z+ ~: V, i(B) specific responses of various species to chemical signals+ D* ^8 C# C8 I& Y
(C) similarities between two chemical substances
/ {: {1 Z+ X( y1 O; Q(D) how insects produce different chemical substances9 X! l0 G7 D4 h. I# v- |
43. The word "sole" in line 6 is closest in meaning to
- v {) X& v6 `+ w/ J- y$ P(A) obvious- f* s4 ~% s( R; K1 e6 l, E& ?. _
(B) best
% K3 K+ s& J; U6 x6 b7 I0 ^% t(C) only5 [& Z5 F/ I9 j N5 H. e
(D) final8 N4 ~2 I7 Y! `' D
44. The passage suggests that the speed at which communication through pheromones occurs is dependent on how quickly they* p2 q N" N+ ]2 D& m
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/ C4 d5 o D" y$ Z" d+ q, Z(A) lose their effectiveness
2 D8 u2 `3 j9 S/ p: o) f4 ?/ z(B) evaporate in the air
" x- Z, }; h& y) p(C) travel through the air
, D3 [; \) R( \. V- l Y(D) are produced by the body) @% A Q4 L j6 d& T
45. According to the passage, the meaning of a message communicated through a
$ Y4 F0 t9 v- Spheromone may vary when the
+ P; w6 p3 u% _(A) chemical structure of the pheromone is changed5 p) H N3 Z. g, Q6 ~0 C8 Y- c
(B) pheromone is excreted while other pheromones are also being excreted
% x1 k* S+ t+ f4 @(C) exocrine glands do not produce the pheromone
$ K8 N" d- X+ s; o6 {! n! S(D) pheromone is released near certain specific organisms' _* T' B$ _- ~; C3 e* t0 Y$ H
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46. The word "detecting" in line 23 is closest in meaning to
" S# @% }. N6 O, b f$ y(A) controlling
9 Q0 q4 C2 _5 a) i8 x! Q5 X3 t) v(B) storing5 R7 y7 Z: g% S7 C! D, w) S
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(C) questioning |
发表于 2012-8-14 22:34:35
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