The Energetics of Life

Part Two: Practice

Big Questions

How do the energy requirements of life affect the life strategies of organisms?

How do the energy requirements of life affect the structures of populations and ecosystems?

Matter and Energy Are Required

energy

energy

energy

Life is a highly ordered system.

The energy needs of life• Organisms are endergonic systems

– What do we need energy for?• synthesis

–building biomolecules• reproduction• movement• active transport• temperature regulation

How is order maintained?• Life is built on chemical reactions that

transform energy from one form to another• Constant energy input is required

organic molecules ATP & organic molecules

organic molecules ATP & organic molecules

sun

solar energy ATP & organic molecules

The inevitable result of loss of order….

Which must be greater in a living system?

This? Or This?

The Calculus of LifeIf:More food than energy expenditure.Then:Order maintaned Growth (Reproduction)If:More energy expenditure than food.Then:Order lostDiseaseDeath

Organisms must regulate metabolism

2 Major Strategies in animals:Endothermy: Using energy from metabolism to maintain body temperature. (Birds and Mammals)

Ectothermy: Using external thermal energy to help regulate and maintain body temperature. (all other animals)

Heat exchange between an organism and its environment

Radiation is the emission of electromagnetic waves by all objects warmer than absolute zero. Radiation can transfer heat between

objects that are not in direct contact, as when a lizard absorbs heat radiating from the sun.

Evaporation is the removal of heat from the surface of aliquid that is losing some of its molecules as gas.

Evaporation of water from a lizard’s moist surfaces that are exposed to the environment has a strong cooling effect.

Convection is the transfer of heat by the movement of air or liquid past a surface, as when a breeze contributes to heat loss

from a lizard’s dry skin, or blood moves heat from the body core to the extremities.

Conduction is the direct transfer of thermal motion (heat) between molecules of objects in direct contact with each

other, as when a lizard sits on a hot rock.

Every Choice Has Its Consequences

Endothermy:

Advantage:Prolonged periods ofHigh metabolism

Trade-off:Need to more food intake

Every Choice Has Its Consequences

Ectothermy:

Advantage:Decreased metabolic load

Trade-off:At the whim of the environment

The relationship between body temperature and environmental temperature in an aquatic endotherm and ectotherm

River otter (endotherm)

Largemouth bass (ectotherm)

Ambient (environmental) temperature (°C)

Bod

y te

mpe

ratu

re (

°C)

40

30

20

10

10 20 30 400

Maximum metabolic rates over different time spans

Max

imum

me

tab

olic

ra

te(k

cal/m

in;

log

sca

le)

500

100

50

10

5

1

0.5

0.1

A H

A H

A

AA

HH

H

A = 60-kg alligator

H = 60-kg human

1second

1minute

1hour

Time interval

1day

1week

Key

Existing intracellular ATP

ATP from glycolysisATP from aerobic respiration

What about Reproduction?Reproduction (and rearing of offspring) require even more energy than what is needed for normal maintenance and growth.Different reproductive strategies for different circumstances.

All of them take advantage of seasonal energy availability.

Babies are had in spring (roughly speaking).

Reproducing Whales• Whales feed at one end

of their migration range, and mate/calve at the other end (a year apart from each other).

In winter (warm water):• The young nurse from

their mothers.• The mothers live on

stored energy (blubber)

Size does matterA general, inverse relationship exists between the size of an organism and its metabolic rate

Energy budgets for four animalsEndotherms Ectotherm

Ann

ual e

nerg

y ex

pend

iture

(kc

al/y

r) 800,000Basal

metabolicrate

ReproductionTemperature

regulation costs

Growth

Activitycosts

60-kg female humanfrom temperate climate

Total annual energy expenditures (a)

340,000

4-kg male Adélie penguinfrom Antarctica (brooding)

4,000

0.025-kg female deer mousefrom temperateNorth America

8,000

4-kg female pythonfrom Australia

Ene

rgy

expe

nditu

re p

er u

nit m

ass

(kca

l/kg•

day)

438

Deer mouse

233

Adélie penguin

36.5

Human

5.5

Python

Energy expenditures per unit mass (kcal/kg•day)(b)

How does free energy affect Populations and Ecosystems?

What aspects of an ecosystem are most affected by changes in the free energy present in the ecosystem?

What are some examples of changes to ecosystems that could affect the free energy present in the ecosystem?

How can these changes affect the ecosystem?

Deforestation on the Island of Borneo (extrapolated to 2020)

We’re cute because We HAVE to be!Any questions?

Review Questions

1. Here you see Franklin and Zwiebel, as younger cats:

Even now, Franklin is 17 pounds, and Zwiebel is 7.Propose an explanation based on energetics.

2. White nose disease is a fungal infection in bats. During the last few years, bat populations have decreased significantly in the North east due to white nose disease. Researchers believe that the major affect of the fungus is that it interrupts the bats normal hibernatory cycle.

Why would a disease that wakes bats from hibernation lead to the regional decline of bat populations?

3. Proposed:All factors that we have discussed that affect population size ALSO affect the free energy content of the population.

Agree or disagree?

Explain: Food availability & natural disasters, in term of free energy effects.