JK-TK/Newdata huggingface dataset:
Their teeth are differentiated into four types (heterodont dentition). They have external ear-pinna. Most have sweat glands. They have a diaphragm that separates the body cavity into thoracic and abdominal. Other Characteristics
Internal fertilisation - most give birth. They have a double circulatory system with a four-chambered heart. They are endothermic (homoiotherms) . Eg Duck-billed Platypus (egg-laying mammal)
Eg.Kangaroo (pouched mammal)
The young are born immature and are nourished in a pouch with milk from mammary glands. Placental Mammals
They give birth to fully developed young ones which are fed on milk from mammary glands. Some are aquatic. e.g. dolphins, whale,
Others are flying e.g, bat;
Most are terrestrial e.g. rabbits, elephants, buffalo, giraffe, antelope, cow, human being. Placental mammals are divided into various orders:
Rodentia: e.g. rats, mice - have one pair 9f upper incisors. Insectivora: e.g. mole-they are like rodents:
Carnivora: e.g. dog; lion - flesh eaters, they have long pointed canines. Cetacea: e.g. whales and dolphins Aquatic mammals. Forelimbs are flippers. Chiroptera: e.g. bats - Forelimbs form wings. Artiodactyla: e.g. antelopes, cattle - they are even toed with split hooves. Perissodactyla: e.g. horse, donkey - they are odd toed with hooves. Proboscidea: e.g. elephant - upper lip and nose elongated to form trunk. Lagomorpha: e.g. rabbit, hare - mammals with upper and lower incisors. Have larger hind legs than forelegs. Primata: e.g. gorilla, orang utang, chimpanzee, monkeys - some are arboreal, with hand and foot for grasping. Human - Homo sapiens - upright gait, opposable thumb hence use of tools. Construction and Use of Dichotomous Keys
Biological keys are sets of statements that act as clues leading to the identification of an organism. By following the keys we can be able to place an organism in its group. The most common key is the dichotomous key.
Construction and Use of Dichotomous Keys
Biological keys are sets of statements that act as clues leading to the identification of an organism. By following the keys we can be able to place an organism in its group. The most common key is the dichotomous key. This is a biological tool for identification of unknown organisms. The word dichotomous means branching into two. A single characteristic is considered at a time. Two contrasting statements are put forward to describe the characteristics in such a way as to separate the organisms. This continues until all the organisms have been identified. Rules Used to Construct a Dichotomous Key
Use morphological characteristics as far as possible e.g. type of leaf - simple or compound. Select a single characteristic at a time and identify it by number. 1. Type of leaf. . Use identical forms of words for two contrasting statements e.g.:
Flowers scented. Flowers not scented. Start with a major characteristic that divide the organisms into two large groups then proceed to lesser variations that would separate the organisms further into smaller groups. Use positive statements especially the first one. Avoid generalizations e.g. short plants. Be specific in your description e.g.:
plants above 1m tall. plants below 1m tall. Some Common Features Used for Identification
In Plants
Leaves
Type of leaf Leaf
(a) Compound leaves. (b) Type of venation. Simple leaf
Trifoliate
Pinnate
Type ofleaf margin. Type ofleaf arrangement on stem. The colour of leaf. The texture ofleaf; whether hairy or smooth. Shape of the leaf e.g. palmate. Stem
Type of stem - woody or herbaceous. Shape of stem - cylindrical or rectangular. Texture of stem smooth or spiny. Infloresence
Are flowers terminal or lateral
For each flower:
Is the flower regular or irregular? Number of floral parts for each whorl. Are floral parts free or fused? Roots
Type of root system- Taproot or fibrous? Function of the root. In Animals
Features used to identify animals:
Type of mouthparts. Type of skeleton. Presence or absence of antennae. Body segmentation. Body covering: scales, fur, hair or feathers. Number of body parts. Locomotory structures: legs, wings and fins. Presence or absence of vertebral column. Presence and type of eves.
Locomotory structures: legs, wings and fins. Presence or absence of vertebral column. Presence and type of eves. Practical Activities
To examine Bryophyta
A mature moss plant is obtained. The specimen is observed using a hand -lens. A labelled drawing showing structures is made: rhizoids, set a capsule, gametophyte, sporophyte .. To examine Pteridophyta
A mature fern plant is obtained. It is observed using a hand lens. Sori can be seen on the lower side of fronds. A labelled drawing showing: frond, pinna, sorus, rhizome and adventitious roots. To examine Spermatophyta
A mature twig of either cypress or pinus with cones is obtained. Observation of Male and female is made using a hand-lens. The naked seeds are noted. The leaves show xerophytic characteristics e.g. they are rolled, or needle-like. A mature bean plant with pods is obtained,
Observation of the leaves, stem and roots is made. Leaves are compound, broad arid have network of veins. The Ieaf-has a leaf stalk. They have a tap root system. Floral parts are in five e.g. 5 petals. A bean seed has two cotyledons. A mature maize plant is obtained. Observation of the leaves, stems and roots is made. Leaves are simple, narrow and long with parallel veins .. The petiole is modified to form a leaf sheath. They have a-fibrous root system. Floral parts are in threes. A maize gram has one cotyledon,
Examination of Arthropoda
Specimens of crayfish, millipede, centipede grasshopper and spider are obtained. Where specimens are not available photographs are used. External features of the specimens are observed. The differences in the following are noted:
Body parts. Antennae. Other appendages. Eyes. Examination of Chordata
The following specimens are obtained:
Tilapia, frog, Lizard, bird and rabbit. Using observable features each specimen is placed into its class. Features used include:
Body covering. Limbs. Type of teeth. END
ECOLOGY
Introduction
Ecology is the study of organisms and their environment. All organisms show interdependence on one another. Organisms are affected by their environment, and they in turn affect the environment.
END
ECOLOGY
Introduction
Ecology is the study of organisms and their environment. All organisms show interdependence on one another. Organisms are affected by their environment, and they in turn affect the environment. Green plants manufacture food by photosynthesis which other organisms obtain directly or indirectly. Growth of plants is mainly affected by environmental factors such as soil and climatic factors. On the other hand, organisms modify the environment through various activities. This interrelationship comprises the study of ecology. The study of ecology is important in several fields of study such as agriculture and environmental studies. Concepts and Terms Used in Ecology
Habitat:
This is the place or "home" that an organism lives or is found,
e.g., forest or grassland. Niche:
A niche is the functional unit in the habitat. It includes not only the specific place in which an organism lives but also how the organism functions. To avoid or reduce competition, organisms are separated or segregated by their niches,
for example, different species of birds make their nest on one tree, some at tips of terminal branches, and others feed on leaves, some on flowers and yet others on fruits of the same tree, i.e., food niche. Yet others feed on same food, e.g., worms in the same place but at different times - time niche. Population:
The term population refers to the total number of individuals of a species living in a given area at a particular time. Density is the number of individuals of a population found in a unit area, i.e.,
Dispersion:
This is the distribution of individuals in the available space. Dispersion may be uniform as in maize plants in a plantation;
random as in cactus plants in the savannah ecosystem or clumped together as in human population in cities. Community:
This is the term used to describe all the organisms living together in an area. During the development of an ecosystem, the species composition of a community changes progressively through stages. Finally a steady state is reached and this is described as the climax community. This development of an ecosystem is termed succession. Each stage in development of an ecosystem is a sere. Succession is primary when it starts with bare ground, and secondary when it starts in a previously inhabited area e.g. after clearing a forest. The Ecosystem:
The community and the abiotic or non-living environment together make up an ecosystem or ecological system.
Succession is primary when it starts with bare ground, and secondary when it starts in a previously inhabited area e.g. after clearing a forest. The Ecosystem:
The community and the abiotic or non-living environment together make up an ecosystem or ecological system. In this system energy flow is clearly defined from producers to consumers and nutrient cycling takes place in paths that links all the organisms and the non-living environment. Biomass:
This is the mass of all the organisms in a given area. Ideally, it is the dry mass that should be compared. Carrying capacity:
This is the maximum sustainable density in a given area e.g. the number of herbivores a given area can support without overgrazing. Factors in an Ecosystem
Abiotic factors (environmental factors)
Temperature
Is the hotness or coldness of an area or habitat. It directly affects the distribution and productivity (yield) of populations and communities. Most organisms are found in areas where temperature is moderate. However, certain plants and animals have adaptations that enable them to live in areas where temperatures are in the extremes such as the hot deserts and the cold polar regions. Temperatures not only influence distribution of organisms but also determine the activities of animals. High temperature usually accelerates the rates of photosynthesis, transpiration, evaporation and the decomposition and recycling of organic matter in the ecosystem. Light –
Light is required by green plants for photosynthesis. Light intensity, duration and quality affect organisms in one way or another. Atmospheric Pressure
The force per unit area of atmospheric air that is exerted on organisms at different altitudes. Growth of plants and activity of animals is affected by atmospheric pressure
e.g., rate of transpiration in plants and breathing in animals. Salinity
This is the salt content of soil or water. Animals and plants living in saline conditions have special adaptations. Humidity
This describes the amount of moisture (water vapour) in the air. Humidity affects the rate of transpiration in plants and evaporation in animals. pH
Is the measure of acidity or alkalinity of soil solution or water. pH is very important to organisms living in water and soil. Most prefer a neutral pH. Wind:
Is moving air currents and it influences the dispersion of certain plants by effecting the dispersal of spores, seeds and fruits. Air currents also modify the temperature and humidity of the surroundings. Topography:
These are surface features of a place.
Wind:
Is moving air currents and it influences the dispersion of certain plants by effecting the dispersal of spores, seeds and fruits. Air currents also modify the temperature and humidity of the surroundings. Topography:
These are surface features of a place. The topographical factors considered include altitudes, gradient (slope), depressions and hills. All these characteristics affect the distribution of organisms in an area
e.g., the leeward and windward sides of a hill. Biotic factors:
These are the living components in an ecosystem,
competition
predation,
symbiosis,
parasitism,
human activities. Inter-relationships Between Organisms
The relationships between organisms in a given ecosystem is primarily a feeding one. Organisms in a particular habitat have different feeding levels referred to as trophic levels. There are two main trophic levels:
Producers:
These organisms that occupy the first trophic level. They manufacture their own food hence are autotrophic. Consumers:
These are the organisms that feed on organic substances manufactured by green plants. They occupy different trophic levels as follows:
Primary consumers:
These are herbivores and feed on green plants. Secondary consumers:
These are carnivores and feed on flesh. First order carnivores feed on herbivores while second order carnivores feed on other carnivores, i.e., tertiary consumers. Omnivores:
These are animals that feed on both plant and animal material. They can be primary, secondary or tertiary consumers. Competition:
This describes the situation where two or more organisms in the same habitat require or depend on the same resources. Organisms in an ecosystem compete for resources like food, space, light, water and mineral nutrients. Competition takes place when the environmental resource is not adequate for all. Intraspecific competition. This is competition between organisms of the same species. For example, maize plants in a field compete for water and nutrients among themselves. Interspecific competition. This refers to competition between organisms of different species, e.g., different species of predators can compete for water and prey among themselves. Predation
It is a relationship whereby one animal (the predator) feeds on another (the prey). Saprophytism
Saprophytism is the mode of nutrition common in certain species of fungi and bacteria. Such organisms feed on dead organic material and release nutrients through the process of decomposition or decay. Saprophytes produce enzymes, which digest the substrates externally. The simpler substances are then absorbed.
Such organisms feed on dead organic material and release nutrients through the process of decomposition or decay. Saprophytes produce enzymes, which digest the substrates externally. The simpler substances are then absorbed. Saprophytes help in reducing the accumulation of dead bodies of plants and animals. Harmful saprophytes cause rapid decay of foods such as fruits, vegetables, milk and meat. Others damage buildings by causing wood rot. Some fungi produce poisonous substances called aflatoxins. These substances are associated with cereal crops which are stored under warm, moist conditions. If the infected grain is eaten, it may cause serious illness, and death. Parasitism
This is an association between members of different species. The parasite lives on or in the body of another organism, the host. The parasite derives benefits such as food and shelter from the host but the heist suffers harm as a result. Symbiosis
This is an association in which organisms of different species derive mutual benefit from one another. Some symbiotic associations are loose and the two partners gain very little from each other. Other symbiotic associations are more intimate and the organisms show a high degree of interdependence. Nitrogen cycle –
Is the interdependence of organisms on one another and the physical environment as nitrogen is traced from and back into the atmosphere
Although nitrogen is abundant in the atmosphere, most organisms are not able to utilise it directly. Some bacteria are capable of converting atmospheric nitrogen into forms which can be used by other living organisms. These bacteria are referred to as nitrogen fIxing bacteria. Symbiotic nitrogen fixing bacteria live in the root nodules of leguminous plants such as beans and peas. Non-symbiotic nitrogen fixing bacteria live in the soil. Nitrifying' bacteria convert ammonia into nitrites and nitrates. Denitrifying bacteria convert nitrates into atmospheric nitrogen. Energy Flow in an Ecosystem
Most of the energy used in an ecosystem is derived from the sun. Solar energy is trapped by photosynthetic plants. It flows through different trophic levels . At each level energy is lost as heat to space and also through respiration. Besides animals lose energy through excretion and defecation. The amount of energy passed on as food from one trophic level to another decreases progressively. The energy in the organisms is recycled back to plants through the various nutrient or material cycles. Food Chains
A food chain is a linear relationship between producers and consumers.
The amount of energy passed on as food from one trophic level to another decreases progressively. The energy in the organisms is recycled back to plants through the various nutrient or material cycles. Food Chains
A food chain is a linear relationship between producers and consumers. It represents the transfer of food energy from green plants through repeated stages of eating and being eaten. Types of Food Chain
Grazing food chain - starts with green plants. Detritus food chain - starts with dead organic material (debris or detritus). Detritivores:
Detritivores feed on organic wastes and dead matter derived from the grazing food chain. Many different types of organisms feed on detritus. They include fungi, protozoa, insects, mites annelids and nematodes. Examples of Food Chains
Green plants~ aphids ~ lady-bird beetle
Green plants ~antelope -lion
Algae ~Tilapia ~ kingfisher
Plant debris ~bacteria -eprotozoa ~ mosquito larva
Phytoplankron-eZooplankton ~ Tilapia
~ Nile perch ~ Human
Food Web
In a natural community, several food chains are interlinked to form a food web. Several herbivores may feed on one plant . Similarly, a given herbivore may feed on different plants and may in turn be eaten by different carnivores. Decomposers
These are mainly bacteria and fungi. These organisms feed on dead organic matter thereby causing decomposition and decay and releasing nutrients for plants. They form a link between the biotic and the abiotic components. Pyramid of Numbers
Refers to the number of organisms in each trophic level presented in a graphic form and a pyramid shape is obtained. The length of each bar is drawn proportional to the number of organisms represented at that level. This is because a herbivore feeds on many green plants. One carnivore also feeds on many herbivores. In a forest the shape of the pyramid is not perfect. This is because very many small animals such as insects, rodents and birds feed on one tree. Pyramid of Biomass
This is the mass of the producers and consumers at each trophic level drawn graphically. Population Estimation Methods
It is important to find or estimate the sizes of the different populations in a habitat. Direct counting or head count which involves the counting of every individual, is not always applicable for all organisms .
Pyramid of Biomass
This is the mass of the producers and consumers at each trophic level drawn graphically. Population Estimation Methods
It is important to find or estimate the sizes of the different populations in a habitat. Direct counting or head count which involves the counting of every individual, is not always applicable for all organisms . e.g., it is impossible to count directly the numbers of grasshoppers in an area. Different sampling methods are thus used. A sample acts as a representative of the whole population. . Sampling Methods
Quadrat Method
A Quadrat is a square, made of woos metal/hard plastic. It can also be established on the ground using pegs, rope/permanent coloured ink, using metre rule or measuring tape. The size is usually one square metre (1M2), in grassland. In wooded or forest habitat it is usually larger, and can reach upto 20 m2 depending on particular species under investigation. The number of each species found within the quadrat is counted and recorded. Total number of organisms is then calculated by, finding the average quadrats and multiplying it with the total area of the whole habitat. The number of quadrats and their positions is determined by the type of vegetation studied. In a grassland, the quadrat frame can be thrown at random. In other habitats of forest, random numbers that determine the locus at which to establish a quadrat are used. Line Transect
A line transect is a string or rope that is stretched along across the area in which all the plants that are touched are counted. It is tied on to a pole or tent peg. It is particularly useful where there is change of populations traversing through grassland, to woodland to forest land. This method can also be used in studying the changes in growth patterns in plants over a period of time. Belt Transect
Two line transects are set parallel to each other to enclose a strip through the habitat to be studied. The width is determined by the type of habitat, i.e., grass or forest and by the nature of investigation. In grassland it can be 0.5 m or 1 m. Sometimes it can be 20 metres or more especially when counting large herbivores. The number of organisms within the belt is counted and recorded. Capture-recapture method
This is used for animals such as fish, rodents, arthropods and birds. The animals are caught, marked, counted and released.
The number of organisms within the belt is counted and recorded. Capture-recapture method
This is used for animals such as fish, rodents, arthropods and birds. The animals are caught, marked, counted and released. For example, grasshoppers can be caught with a net and marked using permanent ink. After sometime, the same area is sampled again, i.e., the grasshoppers are caught again. The total number caught during the second catch is recorded. The number of marked ones is also recorded:
Let the number caught and marked be a. The total number in the second catch be b. The number of marked ones in the second catch be c. The total number of grasshoppers in the area be T. The total number T can be estimated using the following formula:
Total Number =
The following assumptions are made:
No migration, i.e., no movement in and out of the study area. There is even distribution of the organisms in the study area. There is random distribution of the organisms after the first capture. No births or deaths during the activity. After the estimation, the results can be used to show anyone of the following population characteristics:
Density:
Density is calculated by dividing the number of organisms by the size of the area studied. Frequency:
Frequency is the number of times that a species occurs in the area being studied. Percentage Cover:
This is the proportion of the area covered by a particular species. For example, a given plant species may cover the whole. of a given area. In this case the plant is said to have 100% cover. Dominance:
This is the term used to describe a species that exerts the most effect on others. The dominance may be in terms of high frequency or high density. Adaptations of Plants to Various Habitats
Organisms have developed structural features that enable them to live successfully in their particular habitats. Plants found beneath the canopies of trees are adapted to low light intensities by having broad leaves. Xerophytes
These are plants that grow in dry habitats,
i.e., in deserts and semi-deserts. They have adaptations to reduce the rate of transpiration in order to save on water consumption. Others have water storage structures. Adaptations include:
Reduction of leaf surface area by having needle-like leaves, rolling up of leaves and shedding of leaves during drought to reduce water loss or transpiration.