Biological Scaling, Thermoregulation, and Animal Adaptations

heterotroph

An organism that obtains its organic molecules by consuming other organisms or organic matter.

scaling

The study of how biological variables change with size among organisms.

allometry (+, -)

The relationship of body size to shape, anatomy, physiology, or behavior; positive allometry means a trait grows faster than body size, negative allometry slower.

isometry

Growth in which proportions remain constant as size changes.

geometric similarity

When organisms or structures maintain the same shape as they increase in size (isometric scaling).

Meganeura

An extinct genus of giant insects (related to dragonflies) from the Carboniferous, whose large size was possible due to higher atmospheric oxygen.

air sacs in birds

Thin-walled extensions of the lungs that store air and allow unidirectional airflow for efficient gas exchange.

lungs

Internal organs for gas exchange with air, used by most terrestrial vertebrates.

tracheal system (spiracles/tracheae)

Network of air tubes in insects that deliver oxygen directly to tissues through spiracles (openings).

gills

Organs in aquatic animals that extract oxygen dissolved in water.

Herbivore

Animal that eats plants.

grazer

Herbivore that feeds on grasses or low vegetation.

browser

Herbivore that feeds on leaves, twigs, or high vegetation.

granivore

Animal that eats seeds.

frugivore

Animal that eats fruit.

nectarivore

Animal that feeds primarily on nectar.

Omnivore

Eats both plants and animals.

Carnivore

Feeds primarily on other animals.

Detritivore

Consumes decomposing organic material.

Ruminants (foregut)

Herbivores with a multi-chambered stomach for fermenting plant material before digestion.

rumen

The first stomach chamber, where microbes break down cellulose.

reticulum

Second chamber that traps dense particles and regurgitates cud.

omasum

Third chamber that absorbs water and nutrients.

abomasum

The true stomach where enzymatic digestion occurs.

Hindgut fermenters

Herbivores that ferment plant material in the large intestine or cecum.

caecum

A pouch connected to the intestine containing microbes for fermentation.

coprophagy

Eating one's feces to recover nutrients after fermentation.

crop

A storage pouch in the esophagus of birds for holding food before digestion.

proventriculus

The glandular stomach of birds that secretes digestive enzymes.

gizzard

Muscular part of a bird's stomach that grinds food with small stones.

endothermy

Regulation of body temperature by internal metabolic heat production.

homeothermy

Maintenance of a constant internal body temperature.

ectothermy

Reliance on external heat sources for body temperature regulation.

poikilothermy

Variable body temperature depending on environmental conditions.

heterothermy

Combination of endothermic and ectothermic traits; body temperature fluctuates.

operative temperature range

Range of environmental temperatures within which an animal can maintain body temperature.

behavioral thermoregulation

Use of behavior (e.g., basking, shade-seeking) to control body temperature.

thermoneutral zone

Range of environmental temperatures where metabolic rate is minimal for temperature maintenance.

shivering

Rapid muscle contractions that generate heat.

brown fat

Specialized adipose tissue that produces heat via non-shivering thermogenesis.

evaporative cooling

Heat loss through evaporation of water (e.g., sweating, panting).

sweat, pant/gular flutter, wallow

Mechanisms for evaporative cooling — sweat through skin, panting or throat vibration (birds), wallowing in mud/water.

SA/volume

Surface area-to-volume ratio; smaller animals have higher ratios, affecting heat and oxygen exchange.

mass specific oxygen consumption

Oxygen consumption per unit body mass; decreases with body size.

temporal heterotherms

Animals that undergo body temperature changes at certain times (e.g., daily torpor, hibernation).

torpor

Short-term reduction in metabolism and body temperature to conserve energy.

hibernation (vs winter sleep)

Long-term torpor during winter with lowered metabolism; winter sleep (e.g., bears) has higher body temperature and can awaken easily.

supercooling

Process of lowering body fluids below freezing without ice formation.

countercurrent heat exchange

Heat transfer between parallel blood vessels to retain core temperature.

rete

A network of closely arranged vessels for countercurrent heat exchange.

estivation

Dormancy during hot or dry periods to avoid heat or drought stress.

diapause

Developmental or reproductive pause in response to adverse conditions.

population

A group of individuals of the same species occupying an area and interbreeding.

modular organisms

Organisms that grow by repeating structural units (modules), e.g., corals or plants.

unitary organisms

Organisms with a determinate, individual body form (e.g., animals).

stolon

Horizontal stem growing above ground, producing new individuals.

rhizome

Horizontal underground stem that gives rise to new shoots or roots.

genet

A genetic individual originating from a single zygote.

ramet

A physiologically independent module of a genet.

spatial scale

The physical dimension at which ecological processes occur.

geographic distribution

Area over which a species occurs.

mosaic

Patchy spatial pattern of habitats or populations.

environmental heterogeneity

Variation in environmental conditions across space or time.

patchiness

Degree to which habitats or populations are spatially aggregated.

local population

A group of individuals occupying a small area within a species' range.

subpopulation

A distinct breeding group within a larger population.

deme

A local interbreeding population.

geographic barriers

Physical features (mountains, rivers) that prevent movement between populations.

ubiquitous

Widespread; found everywhere.

metapopulation

A group of spatially separated subpopulations connected by dispersal.

abundance

Number of individuals in a population.

density

Number of individuals per unit area or volume.

crude density

Population density calculated using total area, including unsuitable habitat.

ecological density

Density calculated using only suitable habitat area.

population distribution

Spatial arrangement of individuals (random, uniform, clumped).

random

Individuals distributed independently of each other.

uniform

Evenly spaced individuals, often due to competition or territoriality.

clumped

Aggregated distribution due to social behavior or resource patchiness.

quadrat

Sampling unit of fixed area used to estimate abundance or density.

transect

Line or belt along which observations or samples are made.

Lincoln-Petersen index

Mark-recapture formula estimating population size N=(M×C)/R.

index of abundance/density

Relative measure of population size based on indirect indicators.

relative abundance/density

Comparison of abundance among species or areas.

age structure

Proportion of individuals in different age classes.

age pyramid

Graph showing age structure of a population.

sex ratios

Proportion of males to females in a population.

dispersal

Movement of individuals away from birthplace.

emigration

Movement out of a population.

immigration

Movement into a population.

migration

Regular, often seasonal, movement of individuals.

diel

Occurring within a 24-hour period (e.g., day-night cycle).

range expansion

Increase in geographic range of a species.

invasive species

Non-native species that spreads and causes ecological or economic harm.

population growth

Change in population size over time.

open population

Population with immigration and emigration.

closed population

Population with no immigration or emigration.

b

Birth rate.

d

Death rate.

dN/dt

Change in population size over time.

r

Per capita rate of population growth.