Habitat

HABITATS The habitat of an organism is the type of environment or place where an organism live and survive normally. There are two main classes/kinds of habitat, they are aquatic and terrestrial. AQUATIC HABITATS/BIOMES An aquatic habitat is an environment consisting of water which ensures survival of some organisms. Aquatic habitats are divided into three broad divisions, marine or salt water, freshwater and estuarine or brackish-water. There are three main conditions which distinguish freshwater habitat from marine habitat. These are: 1. The salt content of fresh water is very low and that of marine is very high; 2. Strong, swift currents (except ponds and large lakes) are common features of freshwater habitat and marine habitat does not experience strong and swift current; 3. Climate and weather often affect freshwater habitats (except very large lakes) much more easily than marine habitat. The marine habitat As explained above, marine habitat contains high proportion of salt, hence the name salt water habitat. Examples include salt water lake, oceans, the shore and open sea. Characteristics of the marine habitat 1. Salinity is very high and its average is put at 35.2 per thousand. 2. Density of marine water is higher than that of freshwater, hence many organisms can float in it. The density is put on the average of 1.028, while that of freshwater is 1.00 3. Size of marine habitat is very large, occupying more than two thirds of the earth's surface. 4. Pressure in marine habitat increases at 1 atmosphere at the surface to 1000 atmospheres at the bottom. In other words, this means at a depth of about 1000m, the pressure would be about 100 atmospheres. 5. Turbidity is very high due to the suspended particles washed into it from land and rivers. 6. Light can only penetrate to about 200 metres due to high turbidity. Therefore plant life is limited to the upper layers of the ocean where light can penetrate. 7. Dissolved gases are usually oxygen and carbon dioxide. More oxygen are dissolved at the surface due to the wave action at the surface and due to the photosynthetic activities of phytoplanktons; oxygen level reduces as one goes deep in the sea due to increase in turbidity, and hence more carbon dioxide are concentrated at the bottom due to decomposition and respiration of some organisms that inhabit the bottom zones of the sea. 8. pH (hydrogen ion concentration): the pH of the surface water ranges from 8.0 to 8.5. This means that it is alkaline near the surface. 9. Currents are produced at the surface of the ocean by wind actions, rotation of the earth and differences in water density but not strong and swift. A current is a directional movement. 10. Waves: A wave is undirectional movement of water caused by the blowing of winds against the water surface. Wave action is common in marine habitats. Waves bring about mixing of dissolved oxygen. 11. Tides: This is the rise and fall of the ocean water twice a day. It is caused by the gravitational pull on the earth. Tides have huge effects on the lives of organisms living in lagoon and estuaries because high tide fills the lagoon and estuaries with water while low tides makes the water levels fall drastically, hence much water may not be available to some organisms, especially during dry season when the rivers are dried. MAJOR ECOLOGICAL ZONES OF THE MARINE HABITAT The major ecological zones of the marine habitats include: A. Littoral (euphotic) zone: This is the region that extends over the continental shelf to a depth of about 200 metres. The littoral zone can be subdivided into the: 1. splash (supratidal) zone; 2. intertidal (neritic) zone; and 3. subtidal zone; B. Benthic zone: This is the zone beyond the littoral zone, it can extend to a depth of 10 000 metres. The benthic zone can be subdivided into the: 1. bathyal (disphotic) zone; 2. abyssal (aphotic) zone and 3. hadal (aphotic) zone. 1. Splash or supratidal zone: This is really not part of the marine habitat, but of the terrestrial habitat. It is the area where water splashes when the waves break at the shore; it is just above the high-tide mark and is wetted by the spray from the breaking waves. It is exposed and usually moistened by the splashed water. Plants in the splash zone include halophytes such as Sesuvium. Adaptation of Sesuvium include: - Reduced thick leaves for water conservation; - Chloroplasts for photosynthesis. Animals in the splash zone include crabs. Adaptation of crabs include: - Presence of gills for gaseous exchange; - Possession of powerful chelipeds for seizing food; - Possession of exoskeleton to prevent desiccation on land; - Ability to dig hole to water level to escape predator and strong waves. 2. Intertidal or neritic zone: This zone is purely marine zone. It is the zone along the substratum between the high tide mark and low tide mark. Characteristics of intertidal zone: a. It is exposed to drying conditions of the air at low tides and covered by water at high tides; b. It receives abundant sunlight; hence the name euphotic and photosynthetic activity is very high than respiration; c. Water temperature fluctuates; d. Exposed to wave action; e. The substratum is unstable; f. It is about 150 - 190 metres deep. Plants in the intertidal zone include algae such as Kelp and Sargassum. Adaptive features of Sargassum: - Possession of chloroplast for photosynthesis; - Possession of hold fasts for firm attachment to the substratum; - Presence of air bladders for buoyancy; - Presence of mucilage on the body to reduce desiccation during low tide; - Possession of flattened lamina leaves for buoyancy; - Tough/leathery thallus body/flexible stripe to withstand wave action. Animals in the intertidal zone include periwinkles, crabs, barnacles, starfish. Adaptive features of barnacles: - Presence of shell to prevent desiccation during low tide; - Presence of cilia for filter feeding; - Presence of basal disc for attachment to the substratum during low tide; - Ability to clamp down the mantle during low tide to prevent desiccation. Other adaptive features of animals in the intertidal zone includes: - Ability to dig holes/burrows into thin soil substratum to avoid desiccation/drying; - Body fluid isotonic with sea water to prevent loss/gain of water; - Possession of gills for respiration. 3. Subtidal zone: This zone extends from the low tide zone to the end of the continental shelf. It is the zone between the neritic and oceanic. Characteristics of subtidal zone: a. It is about 200 metres deep; b. It is always covered with water; c. It receives sufficient light (euphotic); d. High rate of photosynthesis. Organisms found here are those found in the neritic and some from the disphotic zone. 4. Bathyal zone: This zone extends from the end of the continental shelf down the oceanic. Characteristics of bathyal zone: a. It is about 3000 metres in depth; b. It receives dim light, hence the name disphotic; c. It is the beginning of the deep ocean; d. Slight water movement; e. Photosynthetic activity is low due to low light penetration, while the rates of respiration exceeds those of photosynthesis. Organisms find this place and beyond difficult to survive. Only few animals live in the entire benthic zone. 5. Abyssal zone: This zone extends from the end of the bathyal zone to a depth of 7000m. Characteristics of abyssal zone: a. The water is uniformly cold and quiet; b. Pressure is high; c. No light penetration, hence the name aphotic. d. Primary food production is by chemosynthesis; e. Very little oxygen dissolved. 6. Hadal zone: This zone is the substratum of very deep water, it goes beyond 7000m depth. Characteristics of hadal zone : As in abyssal zone. Animals in benthic zone include cartilaginous fish such as dog fish, sharks and sting rays, and the bony fish such as sardine, barracuda. Adaptation of animals in benthic zone: Cartilaginous fish: - Ability to retain urea in their body to cope with high salinity; hence prevent water loss from the blood by osmosis; - Ability to excrete excess salts from the blood to avoid accumulation of salt than that of the marine water; - Presence of gills for gaseous exchange; - Possession of large liver which contains large amount of oil which gives the fish low density to remain afloat. - Presence of tail for locomotion and fins for steering - Presence of scales on the skin to prevent loss or entry of water into the fish. Bony fish: - Ability to drink salt water continuously to replace the water they are losing by osmosis; - Ability to eliminate excess salt ingested through the special cells called chloride cells; - Presence of gas-filled bladder for buoyancy. Other adaptive features common to all benthic zone animals include: - Possession of large stomachs to store as much food as possible whenever food is available. - Presence of wide mouth with sharp teeth to catch prey. - Presence of fluorescent organs to attract prey, such as the one possessed by the hatchet fish. Food chain in marine habitat Phytoplankton(e.g. Diatoms)→zooplankton(e.g. Paramecium, amoeba, molluscs)→small fish(e.g. Tilapia)→larger fish(e.g. Shark). Note: In the neritic and euphotic zones, producers, consumers and decomposers are present here; in the disphotic and aphotic zones, the consumers and decomposers are found here. The freshwater habitat Characteristics of freshwater habitat: - Contains no significant amount of salt; - The body is relatively small compared to oceans; - There is significant seasonal variation; - It is shallow compared to oceans; - There is greater light penetration to the bottom; - There is varying temperature from surface to the bottom and from morning, afternoon and evening; - Oxygen is usually available in all parts of the water Types of freshwater habitat Freshwater habitats are classified into two main kinds, based on their mobility. These types are: (i) Lentic fresh waters: These are standing/stagnant bodies of water. They do not flow and are calm. Examples include pools, lakes, ponds, dams and swamps. (ii) Lotic fresh waters: These are running/flowing waters which move on a particular direction on land. Examples include rivers, springs, and streams. Characteristics of freshwater habitats 1. Small size: they are relatively small in size. 2. Seasonal variation: they experience significant seasonal variations as some rivers dry up during dry season, and increases during rainy season. 3. Low salinity: they contain very low level of salts, about 0.5% of salt compared to about 3.5% for sea water. 4. Variation in temperature: their temperature varies with season and depth. 5. Light penetration: light reaches almost all depth due to shallowness of the water. 6. Turbidity is usually very high during rainy season due to movement of wastes from land into water. 7. Oxygen concentration: oxygen is usually available in all parts of the fresh water. 8. Currents: current is very common, especially in lotic habitats. This affects distribution of gases and organisms. Ecological zones of fresh water habitats There are two major zones in a lentic fresh water habitat. These are littoral and benthic zones. The littoral zone is the shallow part of the bottom. The benthic zone is the deeper part. The main difference between littoral zone and benthic zone is that the littoral zone has rooted vegetation at its base while the benthic zone with well developed root systems plants in the mud. Assignment: list three differences between littoral zone and benthic zone of freshwater habitat. In lotic freshwater habitats, there are two zones, the pool zone, where the water is relatively slow and calm, and the rapid zone where the flow is fast. Plants in the freshwater zones include deep rooted plants such as: ferns (Naphrolepis), water lily (Nymphaea), water arum (Cytosperma senegalense), commelina grasses and sedges. The floating plants include: Spirogyra, Chlamydomonas, water lettuce (Pistia), duckweeds (Wolffia), water ferns, bladderwort (Utricularia) and bluegreen algae. Animals in the freshwater zones include zooplankton (they are abundant in lentic freshwater), such as Cyclops and Daphnia which are both copepods. Other animals include water skater, Tilapia, cat fish leeches, larvae and pupae of mosquitoes, water snails crustaceans such as crayfish, water scorpion, crabs. Others are amphibians such as toads, frogs, reptiles such as crocodiles, birds such as ducks, heron, and mammals such as waterduck and hippopotamus. Note: Nekton are active animals which can swim against water currents (directional movement). Adaptative features of freshwater plants: - Presence of large air space/parenchyma in roots and leaves to provide support for buoyancy; e.g. Nymphaea/water lily; - Presence of hairs on the leaves to prevent blockage of stomata; e.g. Pistia/water lettuce; - Stomatal pores occur only at the upper epidermis of the leaves to aid transpiration; - Numerous adventitious roots and root hairs to aid water and mineral salts absorption; - Small size of the plant for buoyancy/floating in water; e.g. Lemna/duckweed - Waxy upper surface of the leaf to prevent clogging of the leaf by water; - Long petiole/leaf stalk to support or expose the broad lamina for photosynthesis; - Long flower stalk to expose flower for pollination; - Presence of breathing roots/pneumatophores for breathing/gaseous exchange; - Thin cuticle for absorption of sunlight for photosynthesis - The entire plant is flattened to aid floating, e.g. Lemna/duckweed; - Ribbon-shaped/finely dissected leaves to allow free flow water current, e.g. Hornwort Adaptive features of freshwater animals: - Presence of swim bladders for buoyancy; e.g. Tilapia; - Presence of webbed digit feet for easy swimming/locomotion; e.g. Duck; - Possession of contractile vacuole for osmoregulation; e.g. Protozoa; - Possession of serrated beak for sieving food into the mouth; e.g. Duck; - Possession of long legs to skate on water surface; e.g. Skaters; - Presence of gills for gaseous exchange; e.g. Tilapia. Why green plants are absent at the lower depth of some lake: Light intensity decreases with depth in water bodies, so at certain depths in water, there is no light for photosynthesis to occur. Energy flow in a freshwater habitat: Common aquatic plants suc as Pistia or Spirogyra use energy from the sun to photosynthesis or produce food. This food is eaten by primary consumers or small aquatic animals which would in turn be eaten by bigger aquatic animals or secondary consumers. In the process of feeding, energy flows from one trophic level to another and decreases progressively; dead animals or plants also decompose, hence this leads to energy loss. Food chain in fresh water biome: Diatoms→Fishfry→Tilapia. Spirogyra→Tadpoles→Carps→Kingfishers. Detritus→Worm→Shrimp→Bird. ESTUARINE This is the place/point where a river enters the ocean/sea into which the tides flow, freshwater mixes with saltwater to form a brackish water. Characteristics of the estuarine habitat 1. The land is low lying; 2. The land is flat or has a small gradient towards the sea; 3. Salinity varies as a result of tides and season; 4. Waves and current are mild compared with the sea; 5. There may be overflow of banks, this leads to frequent flooding; 6. It is a disturbed area as a result of tidal flowing in and out of it; 7. Estuary water has lower specific gravity than sea water, hence marine animals which float in sea water may sink and not do well in estuarine water. Note: the main factor affecting distribution of organisms in an estruary is the salinity levels. Plants in estuary include diatoms, algae, red mangrove, white mangrove, bulrush. Animals in an estuary include mudskipper, barnacles, hermit crabs, oyster, lagoon tulip. Adaptive features of red mangrove to estuary: 1. Ability of the seeds to withstand tides, current and wind until it reaches a mud bank; 2. Possession of rootlets to absorb water and mineral salts; 3. Possession of thick leathery leaves to reduce loss of water by transpiration; 4. Presence of spongy tissue with many air spaces in roots to obtain air. Adaptive features of hermit crab 1. Ability to live in the empty shell of a snail to withstand waves and tides action; 2. Its body remains in the shell for protection; 3. It has specially modified legs for holding tightly to the shell; 4. It has physiological tolerance to variations in salinity. Food chains in an estuarine: Phytoplanktons→Barnacles→Fish→Bird. Detritus→Worm→Mollusc→Bird. Detritus→Shrimp→Fish→Bird. TERRESTRIAL HABITATS/BIOMES This is the life on land. Life begins in water, and over time, organisms that were suitably adapted migrated on to land. There are four kinds of terrestrial habitats: marsh, forest, savannah, and arid lands. MARSHES A marsh is a lowland habitat which is flooded or water-logged at all times, and in which grasses and shrubs grow. It is the transitional habitat between the aquatic and terrestrial habitats. It is a treeles land, but rather dominated by grasses, reeds, sedges and water plants. Characteristics of a marsh 1. It is a flat lowland; 2. It has a high relative humidity atmosphere; 3. Its ground is flooded most of the time; 4. It has high rate of decomposition due to increase in decaying organic matter; 5. There is a decrease in oxygen content in the marsh water; 6. The soil is wet, soft and water-logged. Why some marshes are very strongly acidic: The increased rate of decomposition results in decrease in oxygen content of the marsh water. This results in increased anaerobic conditions of the marsh, which results in the release of foul-smelling gases such as hydrogen sulphide and methane which are acidic gases. This results in acidic marsh. Formation of marshes Marshes occur in lowlands near rivers or estuaries where drainage is poor. Marshes may also develop when river overflows its bank to accumulate on the low land area.. a marsh may also be formed by accumulation of debris in a lake, hence turning aquatic habitat into a wet land. Types of marshes There are two major types of marshes. These are: 1. Freshwater marshes: These type of marshes occur in inland. During their formation, rivers overflow its bank and accumulates debris on the lowland to form a wetland. 2. Saltwater marshes: These type of marshes occur along the coastal areas, when salt water along the coast mixes up with freshwater from rivers to form brackish water. Characteristics of salt marsh habitat: - presence of low oxygen; - High salinity; - Soft muddy environment; - Low light penetration; - Its a flat lowland; - Presence of changing water levels; - Swampy/water-logged. Plants that live in the marshes include duckweed/Lemna sp, aquatic fern/Salvinia, water lettuce/Pistia, water arum/Cyrtosperma, white mangrove, red mangrove. Modification/adaptation of plants to salt marsh - Plants grow long roots/numerous roots to hold to substratum; - Possession of stilt roots for anchorage. Animals that live in the marshes include mangrove-crab, lagoon crab, hermit crab, mudskipper fish, oysters, barnacles, toads, frogs and birds (e.g. heron). Evolution of new habitat in the marsh through succession: As sediments and organic deposits raise the bottom of a marsh above the water table, aquatic vegetation will be replaced gradually by shrubs and eventually by a terrestrial ecosystem of upland grasses or forest trees over time. Food chain in marshes Humus→Earthworms→Frogs→Snakes. Flowering plants→Insects→frogs. SWAMP A swamp is a special form of a marsh, where trees are found with the usual grasses and shrubs, which are known to be found in the marsh. Types of swamp 1. Tropical freshwater swamp forests; 2. Temperate freshwater swamp forests; 3. Mangrove swamp forests. Mangrove swamp forest is found in coast especially in states like Delta, Cross River, Rivers, Ogun, Lagos, Akwa-Ibom and Bayelsa. Characteristics of swamp forest 1. It has tall woody trees; 2. Plants mainly have aerial roots; 3. It has evergreen trees with broad leaves; 4. It has high rainfall; 5. Its water is a combination of fresh water and salt water; 6. It has a very high relative humidity. Adaptive features of mangrove plants 1. Possession of prop rots for support in the soft muddy substratum, e.g Rhizophora and Pandanus. 2. Possession of air roots or pneumatophores to take in atmospheric oxygen because the waterlogged soil is low in oxygen content, e.g. Avicennia. 3. Their seeds undergo viviparous seedlings, that is the seeds germinate while they are still on the parent tree, this prevent them from being washed away. FOREST A forest is a plant community in which tree species are dominant, hence forming a biome. The main forest biomes include the tropical rain forests, the temperate deciduous forests and the coniferous forests. Characteristics and climate of temperate forests: 1. Forests mainly of broad-leaved deciduous trees; 2. Trees shed their leaves during the winter (the coldest period; between December and February); 3. Forests are less dense than tropical forests; 4. Sunlight penetrates into the forests enabling the growth of plants at many levels from ground; 5. Moderately wet climate with a dry or a cold season. Characteristics and climate of coniferous forests: 1. Forests of needle-leaved evergreen conifers such as pines, firs and spruces; 2. Forest has two layers --- a dense layer of tall trees forming the upper storey and a layer of shrubs, ferns and mosses forming the lower layer; 3. Few types of trees are found here, unlike the tropical forests; 4. The Forest floor is covered with a thick layer of conifer needles as decomposition is slow at temperatures; 5. Cool temperate climate with light rainfall and snow. Characteristics and climate of tropical rain forests: 1. It is a dense forest with many types of trees, epiphytes and climbers; 2. There is abundant rainfall and an average temperature of 27oC throughout the year; 3. Presence of broad leaves; 4. Presence of buttress roots which give additional support to them and prevent falling due to wind actions; 5. The vegetation has a pattern of arrangement in stores or layers; 6. Presence of tall trees; 7. Presence of a large amount of fallen leaves on the forest floor; 8. Presence of many climbing plants such as epiphytes, e.g ferns. Examples of plants found in the tropical forests include: Mahogany, teak, Iroko, oil palm, liverworts, mistletoe, African walnut etc. Examples of animals found in the tropical forests include: bats, monkeys, snakes, squirrels, birds, lizards, earthworms, millipedes etc. Strata in a tropical rain forest 1. The upper layer/storey is made up of the tallest trees, over 40m tall, called emergents. The crowns of the emergents do not normally touch one another. Examples of plants in this category are Iroko, Obeche, Mahogany etc. 2. The middle layer/storey is made up of tall trees, between 16m and 40m tall. Their crowns touch, forming a continuous canopy below the emergents. 3. The lower layer/storey is made up of small trees, less than 16m tall, which also form a continuous canopy below the second or middle storey. 4. The shrub layer/storey is made up of small trees, 1-5 metres in height. 5. The ground layer or forest floor which consists of shade-tolerant plants, including mosses and ferns. Adaptive features/ adaptations of forest plants 1. Presence of strong tap root system to hold the trees firmly/anchorage and to absorb water. 2. Presence of large amounts of strengthening tissues such as xylem for support. 3. Presence of stomata and lenticels for gaseous exchange. 4. Presence of broad leaves to increase rate of transpiration. 5. Presence of thin barks to increase water loss. 6. Presence of chloroplasts for photosynthesis. Adaptive features/ adaptations of forest animals 1. Presence of prehensile tail tail to climb and hang onto branches, e.g. Climbing Pangolin. 2. Presence of wing-like structures for gliding, e.g. Flying squirrel and gliding lizard. 3. Possession of opposable digits on the hands and feet to climb trees and grasp slender branches, e.g. Chameleon. 4. Ability to change skin colour to match the forest background to escape predators, e.g. Chameleon. 5. Possession of long sticky tongue to catch prey, i.e. Chameleon. 6. Slim elongated bodies to enable balance on branches by coiling, i.e. Tree snakes. 7. Presence of wings to fly to escape predators and search for food, e.g. Birds, bats. 8. Possession of water permeable cuticle to reduce water loss and prevent drying up, e.g. Earthworm and snail. 9. Movement in groups to protect themselves from predators, e.g Apes such as Gorilla. Abiotic factors affecting tropical rainforest 1. Temperature, 2. Rainfall, 3. Relative humidity, 4. Sunlight, 5. pH of the soil, 6. Wind. Food chains in a tropical rain forest habitat Green plants/herbs/shrubs→herbivores/insects/rats/monkeys→carnivores/leopard. Herbs→grasshoppers→Toads→Hawks. Shrubs→Caterpillars→Lizards→Snakes→HawksTrees→grasshoppers→Chameleons. Detritus→Eartwoms→Birds GRASSLANDS OR SAVANNA A grassland is a plant community in which grass species are dominant, but trees and shrubs may be present. It is an intermediary between forests and deserts. Characteristics of grassland 1. The soil is usually sandy. 2. Intense sunshine. 3. Predominance of grasses. 4. Predominance of bush fires in the dry season. 5. Moderate and low rainfall and high temperature. 6. Presence of drought resistant trees due to low rainfall. 7. Presence of short but scattered trees. Types of grassland The major grassland biomes of the world are: 1. The temperate grasslands, 2. The tropical grasslands. The temperate grasslands: This type of grasslands experience low rainfall, a hot wet summer and a cold dry winter. Temperate grasslands include: a. Prairies in United States of America; b. Steppes in Russia and Asia; c. Pampas in Argentina; d. Veldt in South Africa; e. Downs in Australia. The tropical grasslands: This type of grasslands experience a high temperature throughout the year, and a distinct wet season and a dry season. Tropical grasslands are called savannah, such as in West Africa. Savanna/savannah In Nigeria, there are different types of savannah, they include: I. Southern Guinea savannah, II. Northern Guinea savannah, III. Sahel savannah, IV. Derived savannah. Southern Guinea Savannah Location: This biotic community is found in states like Enugu, Kogi, Benue, Kwara, Oyo, Ebonyi, Osun and Ekiti. Characteristics of southern Guinean savanna 1. It is the largest of all the biotic communities in Nigeria. 2. It has moderate rainfall of between 250mm to 500mm per annum. 3. It has tall grasses. 4. Scattered deciduous trees and shrubs. 5. Predominant of bush fires in the dry season. 6. The common tree species are fire resistant. Trees found here include locusts bean trees, shea-butter and Bridellia etc. Animals found here include antelopes, lions, leopards etc. Nothern Guinea Savanna Location:This biotic community is found in states like Plateau, Kaduna, Bauchi, Kano, Taraba, Niger and Adamawa. Characteristics of Northen Guinea Savanna 1. The rainfall is low (100mm to 300mm per annum). 2. Presence of short grasses. 3. It has scattered and short deciduous trees. 4. Presence of short and scattered trees. Trees in this zone include acacia, date palm, silk cotton plants and baobab. Animals include snakes, lizards, deer, lions, antelopes etc. Sahel Savannah Location: This type of savanna occurs only in Nigeria on the eastern tip of Borno State, around Lake Chad, and some parts of northern states such as Yobe, Kebbi, Zamfara, Kano, Sokoto, Jigawa and Katsina. Characteristics of sahel savanna 1. Presence of short grasses and small trees; 2. Low rainfall, which is spread over only a few months of the year; 3. High temperature; 4. Many drought-resistant and scattered plants. Trees in this biome include Acacia spp, date palm, gum arabic. Shrubs found here include Salvadoran persica, Leptadenia pyroteshnica etc. Animals found here include those found in other types of grassland. Derived Savanna This is a type of grassland existing due to human activities such as farming, house construction and bush burning. It is an artificial savannah, which will revert to its original biome (e.g. Rain forest in Nigeria) when human influence is withdrawn. Adaptive features/ adaptations of savannah plants 1. Possession of broad and succulent trunks/barks to store excess water, e.g. Baobab tree; 2. Possession of long roots to search for ground water, e.g. Acacia; 3. Possession of cluster of shoots which protect the buds during burning e.g. Elephant grass; 4. Possession of very small and thick leaves to reduce transpiration e.g. Acacia; 5. Presence of spines on the body of the plant to protect the plant from being damaged by animal, e.g Acacia. 6. Shedding of leaves during dry season to reduce transpiration i.e deciduous plants, e.g. Locust bean tree. 7. Possessionof rhizomes which regenerate new shoots immediately after bush fire, e.g. Spear grass. Adaptive features/ adaptations of savannah animals 1. Presence of chitinous exoskeleton to prevent desiccation and external damage e.g. Grasshopper; 2. Possession of efficient tracheal system for respiration, e.g insects; 3. Ability to burrow into the soil to avoid excessive heat of the sun and fire; 4. Camouflage body colors to escape predators, e.g Zebras, grasshoppers, and giraffes; 5. Movement of animals in group to achieve strength e.g elephants, and lions; 6. Snails retreat into their shells during dry season to prevent desiccation. This is called hibernation. Abiotic factors affecting Savannah 1. Temperature 2. Rainfall 3. Wind 4. Soil fertility. Soil in the grassland are usually fertile as most of the nutrients are not leached because of low rainfall. 5. Low relative humidity 6. High light intensity. Food chains in the grassland Grasses→grasshoppers→Lizards→Hawks. Wood→Termites→Aardvark//anteater→Lynx. Grasses→Zebras→Lions. ARID LANDS OR DESERT HABITATS An arid land is a biome where water is very difficult to obtain, either because it is scarce or because it is frozen. Types of arid lands There are two major types of deserts, they are: 1. Hot arid lands, which are hot deserts and semi-deserts. Examples of hot deserts are Sahara desert (North Africa), Arabian desert and Kalahari deserts (South Africa), Great Australia desert (Australia) and Atacama desert of South America; and 2. Cold arid lands, which are cold deserts or tundra. The desert is found in interior of Eurasia, North America and in Patagonia (South America). Characteristics of hot arid lands 1. The soils are sandy or rocky; 2. Predominance of strong winds; 3. Little or no vegetation; 4. High sunshine; 5. Hot temperature during the day, but become very low at night; 6. Water is very scarce because rainfall is very low (below 250mm per annum); 7. Low relative humidity due to low rainfall, high temperature and scanty vegetation. 8. Presence of ephemeral. These are plants that complete their life cycles from seeds to plants in a few weeks. They are common in the desert, during the brief rainy season. 9. Plants are widely spaced so that each plant has a maximum area from which to draw available water. Note: The main difference between hot arid land and the tundra/cold arid land is that the tundra is very cold and the ground surface is covered with ice throughout the year, except during the short summer. Location of desert biome in Nigeria: Desert biome is located at the northern borders of Sokoto, Katsina, Jigawa, Yobe and Bornu States. Distribution of plants in arid lands or hot deserts The following are examples of plants found in the desert: Euphorbia,Aloe, Cacti and Date palms (occurring around oases; areas where there is a local source of water). Note: Vegetation which is adapted to dry environmental conditions is called xerophytic and such plants are called xerophytes. Adaptive features of xerophytes/desert plants 1. Leaves are reduced to spines to reduce loss of water/transpiration, e.g Cactus. 2. Possession of thick succulent stem and side branches to store water/conserve water, e.g Cactus. 3. Possession of deep root systems to tap subsoil water, e.g Acacia, and Oleander. 4. Possession of waxy, hairy leaves to reduce transpiration, e.g Baobab. 5. Presence of spines to prevent the plants from being eaten up by browsing animals, e.g the spines on the Cactus. 6. Green modified stem for photosynthesis, e.g Cactus. 7. Presence of sunken stomata or hairs on leaves to reduce transpiration, e.g Eucalyptus Distribution of animals in arid lands or hot deserts The following are common animals found in the desert: camel, rats, lizards, zebras, snakes, locusts, ants, moths, butterflies, hedgehog, fox etc. Adaptive features of desert animals or Ways by which animals in arid land are adapted to droughts and high temperature 1. Possession of hard, impermeable body-coverings to reduce water loss from the body surface by evaporation, e.g insects and reptiles. 2. Presence of wax-covered integumentary which are permeable to water at high temperature, e.g insects. 3. Excretion of concentrated liquid (i.e urea; to be excreted by mammals e.g camel) or solid (i.e uric acid, to be excreted by e.g reptiles, birds and insects) wastes to conserve water. 4. Ability to live in burrows during the day to conserve water and come out at night to feed, e.g desert rats. 5. Ability to live on dry seeds, hence to get the water they need from the food(the seeds) e.g Jerboa rat and from metabolic reactions(e.g by absorbing moisture from the air through their outer body coverings, e.g some desert insects) 6. Presence of fringed feet to move rapidly over sand, e.g lizards. 7. Presence of broader and flatter body shapes to allow sidewinding movements and to sink in the sand, e.g snakes. 8. Presence of scales on the body to limit rate of water loss, e.g lizards and snakes. 9. Possession of muscular nostrils that can close during a sandstorm to prevent entering of dusts into its nasal cavity, e.g Camel. Food chain in arid land habitat Grasses→grasshoppers→Lizards→Snakes. Plants→Ant-lions→Scorpions→Snakes. Factors affecting arid lands/Sahara desert: The following are abiotic factors affecting arid lands: 1. Low rainfall. 2. High temperature. 3. Very low relative humidity at noon but high at night. 4. Strong winds. 5. Intense sunlight.