BIO 107 Lecture 2

THE INDIVIDUAL AND THE INDIVIDUAL AND ITS ENVIRONMENTITS ENVIRONMENT

Ecological Conditions and Ecological Conditions and

Limiting FactorsLimiting Factors

Instructor: Angeli A. Valera – Mag-aso

All organisms are limited in their

distribution by abiotic factors

• Each organism has a range of

conditions within which it can survive

• If conditions are outside this range

the organism cannot survive

Organisms occupy a wide rage of

conditions

• Arctic and Antarctic (Temp < - 40 °C)

• Deserts and tropics (Temp >+40 °C)

• Extreme conditions in thermal vents support extensive biological support extensive biological communities

• Water temperature 400 °C

• Extreme pressure prevents boiling

• No light

Niche

• The range of conditions to which a species is adapted is called its ecological niche

• Different species will evolve different adaptations depending on the adaptations depending on the environmental conditions they face

• As a result, different species will tolerate different ranges of environmental conditions depending on their evolutionary history

Species coexist

• Because they are adapted to different conditions

• They occupy different niches

• No single species dominates everywhere • No single species dominates everywhere because conditions vary from place to place

Fundamental Niche• the range of conditions to which a species

is adapted

� range of conditions actually occupied by a � range of conditions actually occupied by a species

� often smaller than fundamental niche

� as organisms approach the extremes of their tolerances, they may be able to tolerate the conditions but they are often inferior competitors

Niche

Limiting Factors

•define the viability of life.

•Only one limiting factor need be out of its optimum range to

cause stress for an organism.

•Each factor necessary for survival has an ideal range.

Zones of Stress

Each factor has a range of values that are above or below Each factor has a range of values that are above or below

the ideal but not outside the range allowing survival.

Limits of Tolerance

Each factor has an upper and a lower limit beyond which the

organism cannot survive.

Range of Tolerance Each factor has a range of values that

includes the zones of stress and the optimum levels. These

values do not include the upper or lower limits beyond which

the organism cannot survive.

Quantities of any

single factor above or

below optimum levels

necessary for

Law of Limiting FactorsLaw of Limiting Factors

necessary for

organism growth,

reproduction, or

survival will limit

growth, reproduction,

or survival.

Temperature Relations

CONCEPTS:

• Most species perform best in a fairly narrow range of temperatures

• Many organisms have evolved ways to compensate for variations in environmental temperature by regulating body temperature

• Many organisms survive extreme temperatures by entering a resting stage

Heat-shock proteins (Hsps)

Animals living in hot deserts are at risk of overheating,

which results in denaturation of enzymes and other

essential proteins.

Levels of Hsps in cells rise rapidly after exposure to

abnormally high temperatures, Hsps are important abnormally high temperatures, Hsps are important

for species at risk of exposure to high T a because of

their role as chaperone proteins that ‘rescue’

proteins whose tertiary structure has been disrupted

by overheating.

Chaperone proteins bind to denatured regions of a

protein and alter the misfolded structure so that the

correct three-dimensional structure is regained.

Temperature and Bacterial Activity

Thermophilic bacteria = heat-loving

Human vs. Thermophile

high temperature causes cell membranes

to leak and enzymes to stop working

ATPase activity plotted against temperature for four species of lizard

Since Dipsosaurus has enzymes that are stable even at high

T b it needs to expend less energy for thermoregulation

Regulating body

temperature:

Heat transmittance

Acclimation = involves physiological, not genetic changes in

response to temperature; generally reversible with changes in

environmental conditions.environmental conditions.

Metabolic Heat = energy released by an organism during the

process of cellular respiration

Conduction = movement of heat between objects in physical

contact

Convection = process of heat flow between a solid body and a

moving fluid/ wind

Radiation = heat transfer through electromagnet ic radiation

Evaporation = heat loss by an organism

Temperature Regulation

by Plants

DESERT PLANTS

•Decrease heating by

conduction: leaves far

enough above groundenough above ground

•Increase rates of convective

cooling: small leaves

•Reduce rates of radiative

heating: orient leaves parallel

to sunlight, reflective leaves

Temperature Regulation

by Plants

ARCTIC and ALPINE PLANTS

• Increase rate of radiative heating: leaves absorb light , oriented perpendicular to sun’s rays, “cushion” growthsun’s rays, “cushion” growth

• Decrease rate of convective cooling: compact, hemispherical growth form (decrease exposure to surface wind )

• Many evolved to do both= can heat up to temperatures above that of air

Sun-tracking behavior of Dryas

Air temperature=15 °C Sunlight reflected

inward by parabolic-

shaped flowers heats

interior

Sun tracking by

Dryas flowers keeps

Flower

temperature=25 °C

Dryas flowers keeps

flowers facing the

sun for several hours

each day

Basking insect

temperature=25 °C

Temperature Regulation

in Animals

• Poikilotherms = cold-blooded

=temperature varies directly with environment

• Ectotherms = rely mainly on external sources

• Homeotherms = warm-blooded

=endotherms that use metabolic energy to

maintain a constant body temperature

• Endotherms = rely heavily on internal

metabolic heat energy

• Heterotherms =may regulate by endothermy/

ectothermy

High Temperature

The gradients of temperature across the coat of (a) open-

woolled Awassi sheep, (b) short-coated camels and (c)

Merino sheep with dense fleece. All the animals are

exposed to sunlight as shown and T a of 40°C

Heat exchange with the environment in a

terrestrial reptile on a hot sunny day

Temperature and Pigmentation

Costs and benefits of homeothermy

• Costs

• Increased energy requirements

• Increased susceptibility to thermal stress

• Benefits

• Ability to be active in otherwise

inhospitable environments

• Freedom from dependence on sunlight to

regulate body temperatuure

• Increased ability to sustain a high level of

activity

A diagram of a temporal counter-current heat exchanger: the nasal heat exchanger. Inspired air draws heat and water from the walls of the respiratory tract (i) and gives both back again at exhalation (ii). The figures represent approximate temperatures varying from those in the deep body tissues (40°C) to those near the surface. The red arrows show the direction of heat transfer

Simplified diagrams of the venous drainage from the nasal regions and the arterial supply to the

brain and nose in (a) a monkey and (b) an oryx

•The operation of the

nasal counter-current

heat exchanger.

Temperatures (°C)

within the dog's nasal

passages and at the

mucosa during

inhalation and

exhalation indicate the

conservation of heat

when the mouth is

closed. The small

arrows show the arrows show the

direction of heat

transfer from the

mucosa to the air on

inhalation (a) and in

the reverse direction at

exhalation (b)

•Bypass of the dog's

nasal counter-current

heat exchanger by

opening the mouth, an

indication of how heat

loss is enhanced.

Balancing heat gain against heat loss

Decreased heart rate

Shivering suppressed

Respiration rate reduced

Oxygen consumption

reduced

Vasoconstriction of

periphery

Countercurrent heat exchange

in marine organisms

Behavioural thermoregulatory

strategies

Water Relations

CONCEPTS:

• The movement of water down concentration gradients in terrestrial and concentration gradients in terrestrial and aquatic environments determines the availability of water to organisms

• Marine and freshwater organisms use complementary mechanisms for water and salt regulation

A gradient of water potential

Water potential = concentration gradient of water plus other factors

related to water movement

Water Regulation

Terrestrial plants and animals regulate

their internal water by balancing water

acquisition against water loss

• Regulation by terrestrial animals:

Wia = Wd+Wf+Wa-We-Ws

• Regulation by terrestrial plants:

Wia = Wd+Wf+Wa-We-Ws

Wip = Wr+Wa-Wt-Ws

Root pressure

Roots absorb water from the soil by

osmosis or diffusion. Once the

water is inside the roots, it travels

either through the intercellular

spaces or from cell to cell and

ultimately enters the xylem. Thus, the ultimately enters the xylem. Thus, the

xylem in the root develops a positive

water potential and the water is

pushed up the tubes formed by the

xylem elements. The pressure with

which the water is pushed up by the

xylem of the roots is called the

root pressure.

Pathway of Water from the Soil into the Xylem

Root pressure explains the transport of water to the leaves and other parts in the case of short plants like the herbaceous plants. herbaceous plants. However, in tall trees the root pressure (about 1 atmosphere) is not sufficient to send the water up to the leaves. In these trees, transpiration pull transports water.

Wilting and the Transpiration Stream

Transpiration pull results in a continuous

stream of water called the transpiration

stream= a continuous stream of water

extending from the xylem of the leaves to

the xylem of the roots. Transpiration pull

can occur only when there is a continuous

column of water. This continuity is

maintained by the cohesive and adhesive

properties of water.

Adhesion= causes the water molecules to

adhere to the xylem walls

Cohesion= water molecules remain

together and move up as a stream.

Any break in this column, makes ascent of

sap difficult. When a stem is cut, the water

column moves away from the cut end of

the xylem making conduction of water from

the cut end difficult.

Experiments to Prove that Water Rises Upwards in the Plant Through Xylem

Soil moisture and root

development

Dense network

of deeply

penetrating

roots

Sparse

network of

shallow roots

roots

Fog harvesting by a beetle

Classification of desert animals based on body size and rate of evaporation

Cutaneous Evaporative Water Loss

Sweating, an extreme form of CEWL in mammals, is important for cooling in

many species. Sweating is the secretion of water plus some salts from special

sweat glands in the skin, which occurs as a response to an increase in T b.

An ecological puzzle

How does a cicada remain active

when environmental

temperatures exceed its lethal

maximum?

EVAPORATIVE COOLING

It compensates for high

evaporative water loss by high rate

of drinking

Disssimilar Organisms with

Similar approaches

Water availability in aquatic organismsWater availability in aquatic organisms

Freshwater

Saltwater

Water and salt balance in aquatic environments

AbioticAbiotic factor: Lightfactor: Light

• Solar spectrum - made up of short wave radiation, light and long wave radiation short wave radiation are cosmic rays, X-rays and ultraviolet rays, which have wavelengths shorter than 0.4mm.

• Ultraviolet radiation: absorbed by ozone layer, only a small fraction reaches the earth's surface;

3 types: uv-C, uv-B and uv-A.

• Light has wavelengths of 0.4 to 0.7 mm and it is called photo • Light has wavelengths of 0.4 to 0.7 mm and it is called photo synthetically active radiation (PAR). The infrared rays have longer wavelengths, longer than 0.74 mm.

• Electromagnetic spectrum of solar radiation:

Effect of Light on Plants•Phenology: timing of seasonal activaties of plant in relation to changes

in environmental condition.

•Sciophytes = shade loving or photophobic plants, which have best

growth under low intensities of light. Examples: beech, spruce, firs

•Heliophytes or photophilous plants = best grow in full sunlight.

Examples: Pine, willows and birch.

•Photoperiodism = actual duration or length of the day (photoperiod) is

a significant factor in the growth and flowering of a wide variety of

plants.

In this basis, angiosperms are divided into 3 categories.

•Long day plants bloom when light duration is more than 12 hrs per

day. Examples: Beet roots, carrot, oats and rye.

•Short day plants bloom when light duration is less than 12 hrs per day.

Examples: Tobacco, Dahlia, hemp and cosmos.

•Day neutral plants show little response to length of day light.

Examples: Cucumber, cotton and potato.

•Heliotropism or phototropism = effect on movement in some plants

- Light promotes the growth in most of the plants by promoting the development of chlorophyll, photosynthesis, photosynthesis, synthesis of growth hormone and stomatalopening.

- Competition, shade tolerance for plants

Effect of Light on Animals

Color

• Differentiate light colours; well marked in fish, birds and primates due to the presence of cones in the retina of the eye.

Pigmentation

• Light intensity induces chemical changes leading to pigment formation in the cells. Cave animals lack skin pigments. If

• Light intensity induces chemical changes leading to pigment formation in the cells. Cave animals lack skin pigments. If they are kept out of darkness they regain skin pigmentation. Tanning occurs in human beings in response to prolonged exposures to bright sunlight.

Bird Migration

• In the northern hemisphere, birds migrate towards the north during spring (increasing photoperiod) and towards the south during autumn (decreasing photo period). It also controls the migration of fishes like eels and salmon.

Light and aquatic LifeLight and aquatic Life

- Photic zone, different

wavelengths for aquatic

organisms

Ground color and Temperature

Biological Rhythms

Circadian Rhythm•Operating on an 24 hours day - night cycle of the earth's rotation. The simplest form of this is the alternating periods of activity and sleep which correlate with dark and light cycle. In this cycle, some animals remain most active at sunrise and sunset times. Such animals are known as crepuscular, some animals are active during the night (nocturnal) but most animals are active during the day time and called (nocturnal) but most animals are active during the day time and called as diurnal.

Circatidal Rhythm•The biological rhythms synchronized with the low and high tides in the sea are called as circatidal rhythms. Thus the organisms living in the inter tidal zone are alternatively submerged and exposed to air. The other rhythms are circa lunar rhythms, semi lunar rhythm and circannual rhythms.

Photoperiod

Effect on Reproductive Activities•Breeding behavior of insects, certain birds and mammals. For example in some birds, gonads become active during summer. Starlings breed in spring (longer photoperiod) while deer breed in autumn (decreasing photoperiod).Effect on Development•Light in some cases, for example in Salmon larvae, accelerates development where as in Mytilus larvae it retards it. development where as in Mytilus larvae it retards it. Metabolism•Light increases the enzymatic activities and general metabolic rate. It also increases photo - oxidation and respiration rates. Animals found in caves have low rate of metabolism.Locomotion•The regulation of speed of locomotion by light is called photokinesis. For example blind larvae of mussel crab moves faster in light intensities. The orientation of animals during locomotion in response to light is called phototaxis. For example Euglena is positively phototacticwhile earthworms, slugs are negatively phototactic.

AbioticAbiotic factor: Windfactor: Wind

• exacerbates the effects of temperature and water losswater loss

• also exerts forces on organisms (waves act in the same manner)

Prevailing wind patterns,

set ocean currents in motion.

• The patterns of wind flow Land

masses can interrupt these

patterns at a local or regional

level.

• Ocean currents are created by the

flow of winds, and cause great flow of winds, and cause great

patterns of circular flow in the

oceans. The Gulf Stream is one

such current. Without the heat in

this mass of water, the climate of

northern Europe would be much

cooler. This would alter the

biological communities found

there.

Abiotic Factor: Pressure

1,400

1,200

1000

800 25.2

24

22.8

22.8

Adiabatic Cooling

800

600

400

200

0 30

28.8

27.6

26.4

25.2

Elevation Temp ºC

CLIMATIC FACTORS

• The properties of temperature, pressure, humidity, rainfall, sunshine and wind in a given place and time is called weather. The average weather conditions of an area, which includes atmospheric conditions, seasons. etc. constitutes the climate. Weather refers to the daily or the climate. Weather refers to the daily or weakly changes, while climate refers to atmospheric conditions over longer periods, such as seasons. The main climatic regions are:

1) Tropical 3) Temperate and

2) Sub tropical 4) Arctic and Antarctic

Climate

• Four abiotic factors determine climate• Sunlight

• Temperature

• Wind

• Precipitation• Precipitation

• Macroclimate• Global, regional, local climate

• Microclimate• Details of environmental conditions in small

spaces• Forest floor

• Under rock or log

• Temperature

is partly

determined by

the amount of the amount of

solar radiation

hitting an area

• Depends on

latitude, angle

of incidence

Seasons are caused by the tilt of the earth as it revolves about the sun.

Water holds heat: Sea & land breezes

Ocean currents

Air circulation

Coriolis Effect

Wind patterns interact with mountains to cause increased rain on windwardsides, rain shadows on leeward sides.

The atmosphere has a tremendous effect on the distribution of plants and animals. Global patterns of circulations affect rainfall patterns and

the prevailing wind directions. Changes in air circulation over the Pacific Ocean can lead to events,

such as El Nino, which have global repercussions (i.e. torrential rains in the Andes and severe drought in Australia)

The physiognomic method = a technique used to analyze climate and elevation. This method describes common characteristics of leaves and forests found in each climate type.

Certain characteristics,

such as smooth margins

indicate a plant is from a

Botanical Climate

Indicators

indicate a plant is from a

tropical to subtropical

climate.

Tropics-Leaf margins between 57% and 89% entire:-Leaves with driptips common on understory evergreens.- Vines are common in the understory

Subtropics-Leaf margins between 39%-55% entire-Broad-leaved evergreens often with conifers and broad -Broad-leaved evergreens often with conifers and broad leaved deciduous.

Warm Temperate-Leaf margins between 30%-38% entire-Broad-leaved deciduous with conifers.-Evergreens present, but not dominant

Cool Temperate-Leaf margins less than 20% entire-Conifer with some broad-leaved deciduous.

Microclimates

Microclimates

Aquatic Microclimates

The Soil

The Soil