BIO 3500PRINCIPLE OF ECOLOGY

5.2: EVOLUTIONARY TRADE-OFFS•PRINCIPLE OF ALLOCATION by

RICHARD LEVINS5.3: TEMPERATURE AND PERFORMANCE

OF ORGANISMSLECTURER: PUAN SITI MARIAM BT MUHAMMAD NORMEMBERS: •SHARIFAH NURUL AINA BT SAYED BURHANUDDIN

UK26335•WAN AZWIRA BT AB GHANI @ WAN AHMADUK26257•NURUL SYAZDIANA BT MOHD ZUKI

UK26258

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.

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.

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.

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.

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)

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.