Notes ECOLOGY ECOSYSTEM A. ADAPTATION - … · Notes (Module: Survival in the Environment) IJSO Training: Survival in the Environment Notes. ECOLOGY Ecology is the study of the interrelationship

Notes (Module: Survival in the Environment)

IJSO Training: Survival in the Environment

Notes

ECOLOGY Ecology is the study of the interrelationship of organisms and their environment. ECOSYSTEM An ecosystem is a stable, self-perpetuating dynamic system formed by interactions among living & non-living components through which energy flows and nutrients cycle. A. ADAPTATION Adaptation is the modification of an organism in its anatomical structure, physiological process or behavioural trait through the process of natural selection (evolution) such that it increases the chances of survival and reproductive success of the organism. 1. Physical Adaptation Certain body parts of an organism become modified to help it to survive in its habitat, e.g. skin color, shape, body covering. 2. Behavioural Adaptation It is the special ways that an organism behaves to survive in its habitat, e.g. cryptic hehaviour. 3. Physiological Adaptation It is the biochemical reactions or processes performed by the systems in an organism, e.g. making venom, secreting slime, being able to keep a constant body temperature. B. HOW ADAPTATION HELPS ANIMALS SURVIVE Examples 1. Adaptations of Desert Animals Problems faced in a desert: desiccation high temperature a) Camels

Problems encountered Adaptations

Desiccation

The kidneys of a camel can produce a very concentrated urine to conserve water of the body.

The humps of camels store fatty tissue. Water is produced when fat is oxidized during respiration. The water gained is known as metabolic water.

Too hot during the day The body of camel is covered with fine woolly coat which can reduce heat gain.

b) Other desert animals Many desert mammals have long appendages to dissipate body heat to the environment, e.g. large ears. Many animals are crepuscular (they are active only at dusk and at dawn) and active only when the temperature is lower. They may hide in burrows or caves during day time.


2. Adaptations of Animals in Polar Regions Problems faced in the polar region: the temperature is too low (both on land and in the sea) a) Polar bears The body of polar bear is covered with a thick layer of fur. The fur is hollow which can trap more air for better insulation. The fur is white which is a good camouflage. Polar bear has blubber (thick fat layer) under the skin for insulation and energy reserve. b) Polar fish, e.g. Arctic cod Antifreeze proteins and glycoproteins are found in fish (also in plants and insects) living in polar regions. These compounds can lower the freezing point of water so as to prevent the formation of ice crystals in the bodies of polar organisms. 3. Defences against Predators a) Camouflage / Cryptic coloration Prey species have evolved body colours and patterns that allow them to blend into the background such that their predators cannot find them easily. e.g. octopus, fish, reptiles b) Warning coloration Animals that are toxic to predators have colours patterns that serve as warning to would-be predators. e.g. yellow-and-black coloration of bees and wasps, monarch butterfly, poison arrow frogs c) Protective armour Animals with protective coats which may be hard shell e.g. clams horny scales e.g. lizards spines e.g. hedgehogs armour coat e.g. turtles. 4. Osmoregulation a) Freshwater fish The salt concentration of freshwater is lower than that of the fish body fluid.

Problems encountered Adaptations Water passes into the fish by osmosis.

Do not drink water. Body covered by scales and a mucus secretion retards the influx of water. Kidneys excrete large amounts of dilute urine.

Salts diffuse out of the fish.

Gill cells actively transport salts from the water into the body.

b) Marine fish The salt concentration of seawater is higher than that of the fish body fluid.

Problems encountered Adaptations Water losses from the fish by osmosis.

Drink seawater. Kidneys excrete small amounts of urine.

Salts diffuse into the fish. Gill cells actively transport salts out of the body.


C. ENVIRONMENT Environment is all the external conditions and factors, living and nonliving (chemical and energy), that affect an organism. Habitat A habitat is a place with a particular set of abiotic factors (physical factors) in which organisms live. e.g. oceans, freshwater stream, estuary, woodland, grassland. A habitat can be subdivided into numerous microhabitats, each with its own particular conditions (micro-climate), e.g. wood crevices, rock pools. 1. Physical Environment The physical and chemical factors (abiotic factors) affecting an organism which includes: a) climatic factors (water, temperature, light and wind) b) topographical factors (altitude, slope and aspect). c) edaphic factors (the soil & its texture, nutrient status, acidity and moisture content) a) Climatic factors i) Light

1) Light intensity – varies with seasons, latitude and weather conditions Effects on plants ~ Light is necessary for photosynthesis. ~ Shady plants have larger leaves to absorb light than sunny plants. ~ High intensity of ultra-violet light may kill phytoplankton near the water surface. Effects on animals ~ High intensity of ultra-violet light may cause skin cancer in animals. 2) Photoperiod – the duration of daily exposure to light Effects on plants ~ It affects the flowering and fruiting of some plants. ~ It breaks seed dormancy hence leading to seed germination. Effects on animals ~ Change in photoperiod indicates the change of season. Photoperiod getting shorter and

shorted means the coming of winter. ~ It affects the reproduction, migration and seasonal colour change of birds and hibernation

of animals since these activities in animals may follow the change of season. 3) Presence of light Effects on plants ~ Growth of plants is affected by the direction of light, phototropism in root and shoot. Effects on animals ~ Some animals are active under dim light condition, i.e. at night. They are called nocturnal

animals, e.g. many mammals, owls. ~ Some animals are active in day time. They are called diurnal animals, e.g. birds. ~ Some animals are active at twilight (during dusk and dawn), they are called crepuscular

animals, e.g. bats.


ii) Temperature – affects the enzyme activities and thus the metabolic activities of organisms. 1) Effects on plants ~ The temperature decreases from the equator towards the North and South Pole. ~ Together with different amount of rainfall, different biomes will be formed at different latitudes. ~ Temperature also falls with increase in altitude. ~ The same trend of change in biomes along the latitudes may also be observed with

increase in altitude.

2) Effects on poikilotherms ~ Within 5 – 35oC, metabolic rate of poikilotherms increase with increase in temperature. ~ At higher temperature, the poikilotherms will hide in burrows or under shady area to

prevent overheating. Some poikilotherms may undergo aestivation. ~ At low temperature, some poikilotherms, e.g. amphibians and reptiles, need to hibernate. 3) Effects on homoiotherms ~ Some homoiotherms living in hot area are very small and have large surface area to

volume ratio for promoting heat loss, e.g. kangaroo rat. ~ Some mammals may have a pair of large ears for greater heat loss. ~ Some mammals may hibernation in winter while birds migrate to warmer area to breed

and feed.

iii) Gases 1) Carbon dioxide ~ dissolves in water affecting the pH of sol water and in turn affects plant growth ~ combines with calcium to form bones and shells of some animals 2) Oxygen ~ essential in aerobic respiration of organisms ~ Terrestrial organisms will not be affected since the atmosphere has a high concentration

of oxygen (21%). ~ Aquatic animals may suffocate or need to escape if the dissolved oxygen content of water

is too low.

iv) Water

1) Effects on the distribution of plants Algae are restricted in water because they lack cuticle. Mosses and ferns are restricted in moist area because they need water for transferring

gametes. Gymnosperms and Angiosperms are fully adapted to the terrestrial environment because

both of them can transfer their gametes without using water. The gametes are transferred via wind or insects. Availability of water can affect the type of dominant vegetation in a place. 2) Effects on the distribution of animals ~ Animals must require a water source for survival. ~ Animals that not well adapted to dry condition on land are restricted to moist areas (e.g.

near water, in damp place, in damp burrows) e.g. earthworms, woodlice, amphibians


~ Some desert animals can still survive without drinking water for a long period of time because they can use the metabolic water obtained from the oxidation of fats stored inside their bodies, e.g. camels.

v) Wind

- Wind affects transpiration of plants by removing moist air from around the leaves, - Trees in persistently windy positions may grow poorly as a result of high transpiration. - Strong wind may break branches of trees.

b) Topographical factors (altitude, slope and aspect) i) Altitude

- Temperature decreases with higher altitude. ii) Slope

- Influences water movement and the amount of erosion - Trees are more difficult to establish on slope that are too steep. - Water drains away more quickly on steep slope, thus reduces the water availability of soil. - Soil erosion is more serious on steep slope; plants of large size cannot grow on thin layer of soil.

c) Edaphic factors (soil & its texture, nutrient status, acidity and moisture content) Soil provides food and shelter for bacteria, fungi, many invertebrates (e.g. worms, insects, mites). Soil provides anchorage, water, mineral salts for plants

2. Living Environment a) Species is a group of organisms that are capable of interbreeding to produce fertile

offspring. b) Population is a group of individuals of the same species living together in a particular area

at the same time and interbreeding among themselves. c) Community

A community consists of all the organisms (plants and animals) living within a defined area or habitat interacting with one another. e.g. forest community – dominant trees, shrubs, herbaceous plants, climbers and creepers and a variety of animals (squirrels, caterpillars, plant bugs, etc.)

d) Niche

Niche refers to the way of life of an organism in its natural surroundings, including its feeding habit and functional role in the ecosystem. e.g. detritivores, herbivores, carnivores (different stages of an organism may have different niche.) Horses, cows, and giraffes are herbivores. Horses and cows have similar niches in their natural habitats and would compete with the other. Cows and giraffes occupy different niches.


e) Biosphere Biosphere is the part of the Earth and its atmosphere in which organisms live and interact with one another and with their nonliving environment.

f) Biome is the terrestrial portion of the biosphere which are large regions characterized by

distinct climate and specific life-forms (especially vegetation) adapted to it. e.g. tropical rain forest, savannah, desert

g) Symbiosis is any intimate relationship or association between members of 2 or more

species. Each of the two interacting species either benefited or harmed.

Relationship Species A Species B Positive interaction

Mutualism + +

Commensalism + /

Negative interaction

Parasitism + Predation + Competition

+ benefited harmed / not affected

i) Competition - 2 or more individual organisms of the same species or from different species attempting to use the same scarce resource in the same ecosystem. For plants, they may compete for light, water, minerals and spaces. For animals, they may compete for food, shelters and mates.

1) Intraspecific competition

It is the competition between members of the same species for the same resources. The competition is very intense.

2) Interspecific competition

Competition between members of 2 or more different species for any limited resources If the commonly used resource is abundant, different species can share them. As the resources are limited, the more the niches of 2 species overlap, the more they compete with one another.

With significant overlapping of niches, one of the competing species must migrate to another place if possible shift its feeding habits or behaviour through natural selection and evolution suffer a sharp population decline become extinct in that area

ii) Predation One species (predator) attacks and kills another species (prey) for food. It is the feeding relationship between two organisms. It is a natural method of quality control, diseased / less fit individuals are killed out. When the populations of the prey and the predator are plotted in a graph: ~ The density of predators is slightly out of phase / there is a time lag behind with the

number of prey. ~ When the number of predators increases, there is a fall in the density of prey. ~ Then the number of predators decreases due to starvation. ~ If predators are removed from an area, the number of prey increases.


iii) Commensalism It is the interaction between organisms of different species in which one type of organisms benefits and the other type is neither having benefits nor harmed.

e.g. Epiphytes are plants that attach themselves to the trunks or branches of large trees. ~ epiphytes gain benefits by having a solid base on which to grow ~ they live in an elevated spot that give them better access to light, water (from humid air

and rain) and nutrients falling from the tree’s upper leaves and limbs e.g. orchids

iv) Mutualism is the type of species interaction in which both participating species benefit

from each other. e.g. lichen – an association of algae and fungi

v) Parasitism is the interaction between species in which one organism (parasite) getting benefits from the other organism (host) and causing harmful effects to the host, e.g. tapeworm.

D. PHYSICAL CONDITIONS AFFECTING AQUATIC ANIMALS 1. Dissolved Oxygen (DO)

A fast running stream has a greater amount of dissolved oxygen than a pool of stagnant water. A water body e.g. stream, river, pond, sea, heavily polluted with organic matter has a very low level of dissolved oxygen. Some species must need plenty supply of dissolved oxygen while some species can tolerate a highly anaerobic condition. Some animals may be able to extract enough oxygen in water even though the DO level is low. Examples: Blood worm (Chironomus larva). It is the larva of midge living in freshwater. The body appears red due to abundant haemoglobin in its blood to get enough oxygen.

Dragonfly nymph preys on small fish and tadpoles. The predatory process dragonfly nymph is very fast; it requires enough supply of oxygen for its fast movement. It only survives in clean freshwater with high content of dissolved oxygen.

2. Temperature

Temperature affects the enzyme activities and thus the metabolic activities of organisms. As the water temperature increases, many aquatic animals (except mammals) increase their metabolic rate; hence their oxygen demands also increase. The solubility of oxygen in water decreases with increase in water temperature; hence there will be less dissolved oxygen in water.

Fungi

provides a habitat for algae; provides moisture, mineral nutrients; protects against desiccation

provides sugars as food

Algae


3. Salinity Salinity is the concentration of halides (fluoride F-, chloride Cl-, bromide Br-, iodide I-) in water.

Freshwater Brackish water Saline water Brine Salinity (%) < 0.05 0.05 – 3 3 – 5 > 5

Salinities affect the distribution of organisms: e.g. corals are only found in seawater of full salinity (~3.5%). In freshwater, there is a net influx of water into the body of aquatic animals. They have to get rid of the excess water, e.g. amoeba forms contractile vacuole to remove excess water. Rain water reduces salinity of surface level of the sea.

4. Acidity (pH)

If the water is too acidic (too much carbon dioxide is present), the growth rate of molluscs will be retarded because the formation of shells of them is more difficult.

5. Turbidity

Turbidity is high if the amount of suspended solid in water is large. The suspended solid may clog the gills of aquatic animals making them difficult to breathe.

6. Water Current

Water current brings along oxygen, food particles, minerals, and carries away wastes. Strong water current may cause dislodgement of some organisms from their habitats and prevent the settlement of planktonic larvae onto suitable substratum. Water current may help the migration of fish and dispersal of gametes and larvae.

7. Substrate a) Soft substrate e.g. mud, sand

Animals may burrow into mud or sand to get shelter so as to stay away from enemies. They may avoid desiccation when the tide is out, e.g. clams, crabs.

b) Hard substrate e.g. rocks, boulders

Animals can find shelters in the crevices of rocks. Some animals have special means to attach themselves onto the rock surface. Examples: Barnacles and oyster cement themselves onto the rock surface. Chitons, limpets, snails have sucker-like foot to attach onto the rock surface and move around to feed.

E. METHOD OF STUDY OF A PARTICULAR ENVIRONMENT 1. Studying the Distribution of Organisms a) Line transect method

A transect line is laid on the study site. Organisms touching the line along each ½ m or 1 m interval are recorded. This method only shows the distribution of the organisms without knowing their abundance but it gives a quick impression of the dominant species.


b) Belt transect method This is a quantitative account of the organisms present along the transect line to examine the distribution and abundance of organisms. A quadrat which is a wooden or metal frame usually of ½ m x ½ m or 1 m x 1m enclosing a sampling area is put along the transect line continuously or at regular intervals such as ½ m or 1 m. Organisms found within the quadrat are identified and counted. The data recorded can be used to plot a distribution graph, e.g. kite diagram.

Kite diagram The y-axis is divided into sections for each organism. The frequency (no.) of each organism is plotted along its own x-axis. The frequency is divided by 2, half of it is plotted above the x-axis and half below it. The points are jointed together to form a polygon symmetrical about the x-axis. e.g. the following table shows the distribution of two species, X (Mosquito larvae) and Y (Mayfly Nymph), in 25cm2 quadrat at 50cm intervals on a transect across a stream. Species

Insect numbers on a transect across a stream Total 1 2 3 4 5

6

X 4 0 0 0 0 2 6 Y 3 5 9 5 3 5 30

c) Measurement of animal populations i) Direct counting It is useful for sedentary animals. The numbers of animals present are count directly. Usually a small sample is counted and multiply up to give the full number. ii) Mark-release-capture It is useful for active animals, e.g. winged insects, nocturnal animals. A large number of the animals are captured and marked. They are then released back into their habitats. After a period of time, a second capture is carried out. The total number of animals captured and the number of animals that are marked are recorded. The population is estimated using the Lincoln index: No. marked in the second capture = no. marked in whole population Total no. of animals caught in the second capture size of whole population


2. Measuring the Physical Factors a) Temperature

Record with a thermometer. Allow the thermometer to stabilize before taking the temperature.

b) pH of water

Record with pH paper or pH meter. c) Salinity of water

Collect a water sample and measure the salinity with a refractometer. d) Relative humidity

Measure relative humidity with the whirling hygrometer (wet bulb and dry bulb thermometers). Record temperatures of the wet and dry bulb thermometers. Calculate the difference and read against the scale to get the relative humidity.

e) Wind speed

Measure wind speed by holding the hand-held wind-meter against the wind. f) Wind direction

Measure wind direction with a wind gauge. g) Light intensity

Measure the light intensities of different micro-habitat with a light probe.

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Notes ECOLOGY ECOSYSTEM A. ADAPTATION - … · Notes (Module: Survival in the Environment) IJSO Training: Survival in the Environment Notes. ECOLOGY Ecology is the study of the interrelationship