Biology

PRACTICAL APPLICATIONS OF GENETICS

Study of genetics has been put into a wide variety of uses encompassing plants and animals and in particular humans. Blood transfusion. Blood groups are genetically determined. As discussed earlier a person of blood group A can only get blood from another one of A or O. In case of emergencies and unavailability of blood, […]

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EVOLUTION – WELL EXPLAINED

EVOLUTION Meaning of Evolution and Current Concepts Evolution is the development of organisms from pre-existing simple organisms over a long period of time. It is based on the similarities in structure and function that is observed in all organisms. All are made up of cells, and similar chemical compounds are present. This indicates that all

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GESTATION PERIOD

What is Gestation Period? The period between conception and birth is called gestation. In humans gestation takes nine months (40 weeks). The embryo differentiates into tissues and organs during this period. Week 1 to 3: Zygote divides to form blastocyst. Implantation takes place. The three germ layers form endoderm, mesoderm and ectoderm. Nervous system starts

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HYDROPHYTES (WATER PLANTS)

What is hydrophytes (water plants)? Water plants are submerged, emergent or floating. Submerged Plants The leaves have an epidermis with very thin walls and a delicate cuticle. They have no stomata. Water is excreted from special glands and pores at the tips. Other adaptations include the following: Presence of large air spaces and canals (aerenchyma)

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BIOLOGY PRACTICAL ACTIVITIES

Ecology is best studied outdoors. Students identify a habitat within or near the school compound, e.g. a flower bed. The quadrat method is used. Observation and recording of the various animals as well as their feeding habits is done. Birds that feed on the plants or arthropods in the area studied are noted through observation

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KINGDOM FUNGI

Multicellular fungi are made of thread-like structures called hyphae (singular hyphae) that form a mycelium. e.g. Saccharomyces cereviseae (bread yeast). Others include Penicillium, Rhizopus, and edible mushroom Economic Importance of Fungi Beneficial Effects of Fungi Some fungi are used as food e.g. mushrooms. Some are decomposers which enhance decay to improve soil fertility – recycling

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GENERAL PRINCIPLES OF CLASSIFICATION

Classification is the science that puts organisms into distinct groups to make their study easy and systematic. Modern scientific classification is based on structure and functions. Organisms with similar anatomical and morphological characteristics are placed in one group while those with different structures are grouped separately. Modern studies in genetics and cell biochemistry are used

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KINGDOM MONERA

General Characteristics Unicellular and microscopic Some single cells ,others colonial Nuclear material not enclosed within nuclear membrane-prokaryotic Have cell wall but not of cellulose. Have few organelles which are not membrane bound Mitochondria absent Mostly heterotrophic, feeding saprotrophically or parasitically,some are autotrophic. Reproduction mostly asexual through binary fission Most of them are anaerobes but others

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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

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KINGDOM ANIMALIA

Most animals move from place to place in search of food. Major phyla are: Platyhelminthes (Tapeworm). Nematoda (Ascaris). Annelida (Earthworm). Mollusca (Snails). Arthropoda Chordata Phylum Arthropoda Distinguishing Characteristics of Phylum Arthropoda They have jointed appendages, which are specialised for various functions. Their body is covered by a hardened exoskeleton made of chitin. It is shed

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KINGDOM PROTOCTISTA

KINGDOM PROTOCTISTA Examples include; Algae such as spirogyra, Chlamydomonas, euglena, Sargassum And protozoa such as amoeba, paramecium and Trypanosoma. General Characteristics They are said to be eukaryotic since their nucleus is bound by a membrane Most are mobile, and use flagella, cilia and pseudopodia. Some are sessile. They reproduce mainly asexually, by binary fission, fragmentation

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SEED STRUCTURE

What is the seed structure? A typical seed structure consists of a seed coat enclosing an embryo. The seed coat is the outer covering which, in most seeds, is made up of the two layers, an outer testa and inner one, the legmen. The testa is thick; the tegmen is a transparent membrane tissue. The

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AQUATIC PLANT STEMS

The water lily, Salvia and Wolfia whose stems remain in water are permeable to air and water. Oxygen dissolved in the water diffuses through the stem into the cells and carbon (IV) oxide diffuses out into the water. Gaseous Exchange in Roots Terrestrial Plants Gaseous exchange occurs in the root hair of young terrestrial plants.

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ADAPTATION FOR SURVIVAL

COMPETITION Competition is the process by which living organisms in the habitat struggle with one another for limited essential needs in the environment. Such scarce resources in plants include; light, space, nutrient and water while animals complete for food, space or mate. Competition finally results in survival of the fittest and elimination of the unfit.

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