1. BIO 3500
PRINCIPLE OF ECOLOGY
5.2: EVOLUTIONARY TRADE-OFFS
•PRINCIPLE OF ALLOCATION by RICHARD
LEVINS
5.3: TEMPERATURE AND PERFORMANCE OF
ORGANISMS
LECTURER: PUAN SITI MARIAM BT MUHAMMAD NOR
MEMBERS: •SHARIFAH NURUL AINA BT SAYED
BURHANUDDIN
UK26335
•WAN AZWIRA BT AB GHANI @ WAN AHMAD
UK26257
•NURUL SYAZDIANA BT MOHD ZUKI UK26258

2. PRINCIPLE OF ALLOCATION
• Principle of allocation underlies some aspects of the concept
of tradeoffs and typically is considered in term of energy.
• All known organisms are adapted to a limited range of
environment condition, at least partially as a consequence of
‘energy limitation’.
• One of those consequences is that energy allocation to one
of life’s function, such as reproduction, defense against
disease or growth, will reduce the amount of energy
available for other function.
• Albert Bennett and Richard Lenski studied the evolution by
microbial population which can go through hundreds of
generations in a week.
• They focused on 24 different lineages of the bacterium
Escherichia coli.

3. Cont….
• E. coli had been grown at 37⁰C for 2000 generations.
• They used this ancestral strain to establish 6 replicate
populations at 4 temperature regimes: constant 32⁰C, 37⁰C,
42⁰C and daily alternation between 32⁰C and 42⁰C.
• Next, Bennett and Lenski used bacterial cells from each of
the 24 populations to establish 24 new populations.
• Which they were all grown at 20⁰C for 2000 generations.
• Then, they compared the fitness of the low-temperature-
selected line with the fitness of the ancestral line at 20⁰C
and at 40⁰C.
• Their measure shows that the rate of population doubling of
a selected line of E. coli compared to that of its ancestral
line.

4. Cont…
2 major results stand out:
The lines grown at 20⁰C had higher +ve fitness at
20⁰C temperature compared to their immediate
ancestors.
The lines that had adapted to 20⁰C had lower
fitness compared to their immediate ancestor when
grown at 40⁰C.
As predicted by the principle of allocation, selection
for higher fitness at 20⁰C had been accompanied by
an average loss of fitness at higher temperature.

6. Temperature and performance of
organism
• The influence of temperature on enzyme function.
• John Baldwin and P. W. Hochachka studied the influence of
temperature on the activity of acetylcholinesterase, an
enzyme produced at the synapse between neurons.
• This enzyme promotes the breakdown of the
neurotransmitter acetylcholine to acetic acid and choline
and so turns off neurons (process critical for proper neural
function).
 Has highest affinity for acetylcholine at 2⁰C: at winter
temperatures. However, the affinity of this enzyme for
acetylcholine declines rapidly above 10⁰C.
 Acetylcholinesterase shows highest affinity for acetylcholine
at 17⁰C, at summer temperatures. However, the affinity of
acetylcholinesterase falls off rapidly at both higher and
lower temperatures.

7. Cont..
• The optimal temperatures for the two forms of
acetylcholinesterase are 2⁰ and 17⁰C.
• Studies of reptiles, especially lizards and snakes, are
offering additional valuable insights into the
influence of temperature on animal performance.
• Widely-distributed species often offer the
opportunity for studies of local variation in
ecological relationship, including the influence of
temperature on performance.
• For example: the eastern fence lizard (Sceloporus
undulatus)

9. Cont..
• Michael Angilletta studied the temperature relations of S.
undulatus over a portion of its range. He determine how
temperature influences metabolizable energy intake or MEI
(nitrogen waste product produced by lizard).
MEI = C – F – U
where, C= amount of energy intake
F= energy lost in feces
U= uric acid
• Angiletta studied two populations from New Jersey and
South Carolina, regions with substantially different climates.
• Since he had determined the energy content of an average
cricket, Angilletta was able to determine the energy intake
by each lizard by counting the number of crickets they ate
and calculating the energy content of that number.
• Lizards from both populations performed best in fairly
narrow range of temperatures.