Faculty of Science

Permanent URI for this community

https://ir.oauife.edu.ng/handle/123456789/974

Browse

Now showing 1 - 20 of 324

Open Access
Ife and Biology
(Obafemi Awolowo University Press, 1972-03-14) Halstead, L. B.
An inaugural lecture is an occasion to survey one's field, to explain what one does, to demonstrate its relevance and to place one's own contributions into their general perspective. It is in fact an opportunity for a kind of academic license. However, today I intend to outline my attitude to Ife, to discuss some general questions, which I believe are important to us and which have implications for Biology at Ife. I shall illustrate my arguments with examples culled from my observations and experiences here, which though local, may I suspect, have relevance to many young universities in this part of the world.
Open Access
Man and Environment - the Nigerian Situation
(Obafemi Awolowo University Press, 1972-05-16) Imevbore, A.M.A
MAN is an organism and his environment includes all things, living and non-living, which influence his life The study of man's relationship with his environment dates back to the time of his emergence as the dominant species on earth. In the beginning was the land, the plants and the animals. Plants and animals respond to the forces of nature and this involves interaction with the environment. During such interaction animals alter their behavior to adapt to changing conditions, but this rarely causes trouble. If they are unable to change, they simply die out, and become extinct. More often than not it is only man that upsets the delicate balances of nature, creating environmental problems. This trouble would of course be overcome if man became extinct. However, this is not a solution I would wish to advocate.
Open Access
Nitrogen Fixation by Soil Algae of Temperate and Tropical Soils
(Plenum Press, 1977) Stewart, W. D. P; Sampaio, M. J.; Isichei, A. O.; Slvester-Bradley, R.
Blue-green algae are common components of the microbial flora of the soil in many parts of the world (7, 8, 18, 30). In the tropics most attention has been paid to their role in rice paddy soils where, free-living (26, 27) and in symbiotic association with the water-fern Azolla (3, 19, 21, 36) they contribute substantial amounts of nitrogen to the ecosystem. In this paper we present information on the occurrence, activity, and factors affecting soil algae from tropical savanna regions of Nigeria and from the Amazon region of Brazil. The findings are compared with observations made on algae from temperate soils in Scotland. These studies complement ones from tropical (e. g. 22, 26, 27, 37) and temperate (e.g. 6, 9, 12, 28) regions.
Open Access
Chemistry in the Economic Development of Nigeria
(Obafemi Awolowo University Press, 1979-10-18) Oke, O. L.
It is possible to ascertain how much curiosity oriented research has contributed to the economic development of an industrialised country by identifying key discoveries with profitable applications and estimating the economic benefit if it was discovered later. We in the developing countries feel that science (especially chemistry) has contributed greatly to the economic development of the industrialised countries and so we assume that expansion of scientific research and teaching (as is done in these: countries) will automatically lead to wealth. We have failed to realise that the majority of these basic sciences derive most of their impetus and motivation from technologies, and also these industrialised countries with only 25% of the world's population have between 80-90% of the world's research power. If we therefore teach the basic sciences the way it is done in these countries without modification, and conduct similar research, it means our products will be more suitable for these countries than ours.
Open Access
Nitrogen Loss by Burning from Nigerian Grassland Ecosystems
(Royal Swedish Academy of Sciences, 1980) Isichei, A. O.; Sanford, W. W.; Rosswall, T.
Nitrogen loss by burning from natural grassland ecosystems in Western Nigeria was studied over a two-year period in three areas, including sites of Andropogon-Hyparrhenia - Schizachyrium-Brachiaria grassland in derived, Southern Guinea and Northern Guinea savanna. The production of aboveground herbaceous material and litter fall of leaves, wood and fruit/seed was estimated and the nitrogen content just prior to burning determined. Final estimates of from 12 to 15 kg ha-1 yr-1 of nitrogen lost by burning were obtained. it is suggested that such loss may be replaced to a considerable extent by rain and blue-green algal crust fixation.
Open Access
Nitrogen Fixation by Blue-Green Algal Soil Crusts in Nigerian Savanna
(1980) Isichei, A. O.
Blue-green algae, many of which are known to be nitrogen fixers, occur on the surface of the soil as crusts. Crusts are masses of algal filaments that grow on top of each other. These blue-green algal crusts were collected from all of the savanna zones of Nigeria in order to estimate the quantitative role they may play in the nitrogen economy of savanna ecosystems. Algae of the genus Scytonema, which are nitrogen fixers, were dominant in all the crust samples collected. Using the acetylene reduction assay, it was found that the crust samples fixed nitrogen 24 h after rewetting and were affected by pH, temperature, light and moisture variations. If sufficient light were available for near maximum photosynthesis, with an algal cover of the soil surface of about 30 % and mean to maximum-fixation during 70 %of the rainy season of 180 days of 10-hour day-length, from 3.3 to 9.2 kg ha-' yr-' of nitrogen would be fixed. This amount would replace much of the nitrogen lost from the grass standing crop as a result of annual burning of the savanna.
Open Access
Laws of Arrangement
(Obafemi Awolowo University Press, 1980-11-18) Segun, A. O.
The topic, laws of arrangement, concerns the most fundamental and inclusive aspects of life sciences. It will deal with' the scientific term, taxonomy a word derived from two Greek words, "taxis" which means arrangement and "nomos" law. A branch of biology which used to be called "natural history" deals with the diversity of organisms within their environment. This is now split into the two separate branches of systematic and ecology. Systematic is involved with the descriptions, classification and all relationships among species. It therefore, includes taxonomy which is the theory and practice of classifying all organisms, both living and fossil, into a grand overall scheme. It should be noted that classification of organism is not the end of a taxonomist's concern, he is also interested in species formation, factors of evolution, structure of natural populations, biogeography, and the entire broad field of comparative biology.
Open Access
Proteins, Nature's Versatile Devices
(Obafemi Awolowo University Press, 1981-02-17) Aboderin, A.
It is our intentions in this lecture to explore some of the unities that characterise life from the intellectual niche of the protein molecule. To the extent that it can be demonstrated that the choice is not a parochial one, but one that belongs, if not at the centre, close to the centre of the phenomenon of life, to that extent will the intention of this discourse have been fulfilled. As is usual in this type of setting however it is fit and proper for me to seek the understanding of both the initiates and the laity, obviously for very different but understandable reasons. Proteins, as nature's versatile devices, function within comparatively macroscopic entities known as cells. As all students of biology and the history of biology are aware, the cell is the basic unit of biological life. As everyone again is aware there are different kinds of cells, In multicellular organisms such as the present lecture, there are brain cells, liver cells, kidney cells, all of which, within the proper observational grid, not only look different but also have different properties and functions.
Open Access
Nitrogen in Savanna Grass and Litter
(1982) Isichei, Augustine O.
grasses are low in nitrogen. This is relayed to the low nitrogen content of the soils: there is decreasing nitrogen in the soil northwards and this is reflected in the grasses. Even in the same environment some species are better accumulators than others. Possible reasons are advanced for this. The Andropogon species and Beckeropsis uniseta are the best known accumulators. There is a well marked seasonality in nitrogen concentration in grass. The below-ground parts have their highest concentration in the dry season, while in the above-ground parts the highest concentration is at the beginning of growth. Litter is important because it is a major means of nitrogen re-cycling. Its pattern of fall and decay in the savanna is discussed. It is emphasized that most of the litter fall is after the annual fires. Nitrogen content of litter varies from site to site but does not show significant seasonal difference.
Open Access
Primary Production in the Savanna
(1982) Isichei, Augustine O.
It is emphasized that there is a dearth of information on primary production in the savanna in spite of savanna occupying nearly 80% of the West African land surface. Known values from the literature of annual primary production are presented. Values range from 150 to 1800g m-2. This range is not totally encompassing as primary production is strongly influenced by local conditions. The methods in use for measuring primary production are reviewed and their applicability to the savanna examined. The factors that affect primary production in the savanna are enumerated and discussed.
Open Access
Relationship of Woody Plants to Herbaceous Production in Nigerian Savanna
(1982) Sanford, William W.; Usman, Sugei; Obot, Emmanuel O.; Isichei, Augustine O.; Wari, Musa
Evidence is presented that a light, high tree canopy leads to greater production of grasses in the Nigerian Guinea savanna than either full exposure or dense canopy. Furthermore, some shading provides a microenvironment where such favoured species as the Andropogons replace such undesirable species as Schizachyrium sanguineum and Hyparrhenia species. The role of trees in open rangeland in relation to mineral cycling and soil maintenance is briefly discussed. It is recommended that the common practice of clearing all trees to improve rangeland is stopped and a low density of large trees, preferably legumes, be maintained.
Open Access
Nitrogen Concentration in the Major Grasses of the Derived and Guinea Savanna Zones of Nigeria in Relation to Season and Site
(1983) Isichei, Augustine O.
The concentration of total Kjeldahl N in above- and below-ground grass samples was monitored at five Nigerian savanna sites over 3 years. Significant variation, even in the same species, was found from plot to plot, with the highest concentrations in the samples from early-burnt Derived savanna and the lowest from northern Guinea samples. This may be related to soil N concentrations as a significant positive relationship was found between soil and plant concentrations. Nitrogen concentration in above-ground grass biomass declined almost exponentially from flushing through the dry season, whereas below-ground N concentration increased with the approach of the dry season. Two shade-favouring grasses, Andropogon tectorum and Beckeropsis uniseto were found to have the highest N concentrations above-ground.
Open Access
Seasonal Succession in a Small Isolated Rock Dome Plant Community in Western Nigeria
(1984) Isichei, Augustine O; Longe, Peter A.
On the slopes of one of the inselbergs within the Univ. of Ife Campus, Western Nigeria (7o32'N, 4o31'E) are islands of vegetation completely separated from each other by expanses of bare rock. The pattern of seasonal succession in one small vegetation island was studied by weekly estimation of species importance. Species importance was estimated by censusing all individuals and by measurements of cover. At the beginning of the growing season the island is dominated by ephemerals which are later replaced by drought enduring perennials. The number of individuals and species and species diversity and abundance patterns on the island over the growing season show a specific pattern which probably occurs every season.
Open Access
Kinetics and Mechanism of Aquation of Tris (3, 4, 7, 8 - Tetramethyl - 1, 10 - Phenanthroline) Iron (II) Suphate in Aqueous Sodium Lauryl Sulphate.
(Obafemi Awolowo University, 1984) Soriyan, Oladega Omopariola; Ige, Jide
In this thesis we report the kinetics and mechanism of the aquation of tris(3, 4, 7, 8-tetramethyl1,10 phenanthroline) Iron(II) sulphate in aqueous micellar solution of Sodium Lauryl sulphate(NaLS). The aquation is inhibited by NaLS in the presence of H+, OH- , SO42- , NH4+ and tetraethylammonium ion (Et4N*). The inhibition is attributed to the stable association or binding between the complex and the micelle and the decrease in the activity of water in the micellar phase. The partitioning of the substrate between the bulk water solution and the micellar phase is in favour of the latter. The kψ-[surfactant] profiles are structured due to micellar evolution. A mechanism which fits kinetic data at low surfactant concentration is proposed. From the rate law obtained and kinetic data observed, the micelle-complex binding constant K1 and micelle-acid binding constant K3 are calculated to be 2.81 x 105 and 13.80 mol -1dm3 respectively in acid medium. Using Scat chard method, K1 in neutral medium is 3.95 x 105 mol-ldm3. The decrease in K1 in acid medium is due to competition for the binding sites on the micelle by the acid proton H+ and the complex ion. The rate of reaction is a function of equilibrium distribution of all the substrates between the micellar phase and bulk water phase. The evolution of the micelle with respect to the c.m.c. is also a function of the nature of the substrate present in solution. Calculated activation parameters suggest strong steric stabilisation of the transition state with respect to enthropy. The magnitudes of activation parameters ΔH# and ΔS# are functions of the surfactant concentration. ΔH# (KJ mol-1) and ΔS# (JK-1 mol-1) for the aquation in 0.00, 1.0 x 10-4 and 2.0 x 10-4 mol dm-3 NaLS are respectively: 100.40 ± 2.04, 22.58 ± 0.16; 111.48 ± 1.15, 48.94 ± 0.09; 119.19 ± 1.15, 67.16 ± 0.09 in 1.00M H2SO4.
Open Access
Pollution Pattern in the Mokuro Dam in Ile-Ife
(Obafemi Awolowo University, 1984) Petters, Hannah Itam; Odeyemi, Olu
Bacteriological and physical-chemical analyses of the Mokuro Jam (in Ile-Ife) an its distribution system were carried out from December 1982 to November 1983 at monthly intervals, and the quality of water was assessed to establish the pollution pattern. Generally, the population density of aerobic heterotrophic bacteria varied between wet and dry seasons., While thorn was an increase in the mean monthly population of bacteria from 4.2 x 102/ml in November to 4.8 x 106/ml in February (i.e. dry season) there was a comparative decrease from 11.0 x 106/ml in June to 1.8 x 103/ml in October (i.e. rainy season), in the distribution system In the stream and in the dam, the seasonal trends of total aerobic bacterial distribution followed more or less the same pattern as in the distribution system. In the dam, the faecal coliform populations ranged from zero to 33 MPN/100 ml during the rainy season and from 2 to 221 MPN/100ml in the dry season. The same pattern was observed in the distribution system. Both faecal streptococci and Clostridium perfringens were also detected in the water samples with no definite pattern of population distribution between the seasons. The mean monthly faecal streptococci ranged from zero to 2.8 x 10 4/mt, while Clostridium perfringens ranged from zero to 538 MPN/100ml. Nitrate, phosphate, chloride and dissolved solid levels were generally low. These compounds ranged from zero to 1.16 mg/l; from zero to 0.038 mg/I, from 3.6 to 54 mg /l, and from 0.0001 to 0.058 g/100ml, respectively. The BOD varied with a range of 1.0 to 12.6mg /l in the dam. In the distribution system, the chlorine residual was generally below 1mg/l, decreasing with distance away from the chlorination point.
Open Access
The World of Bats
(Obafemi Awolowo University Press, 1984-05-15) Okon, Eyo.E
I chose the topic: "The World of Bats" for my Inaugural Lecture for two principal reasons. First, with so much mystery and superstition surrounding bats generally, and with their wide variety of life patterns, coupled with the fact that with some two thousand species or so, bats are the second most numerous mammals (the first being the rodents), the bats are truly a world unto themselves. Secondly, my name is so much linked with bats that it appears that our two names could soon become synonymous. Indeed, when I was promoted professor a couple of years ago, some of the goodwill messages I received contained more compliments to the bats than to me. For example, one of the telegrams I received on that occasion said: "Congratulations to the Bats". I was left out! So, this public lecture affords me a golden opportunity to show that I am in fact the one who has been working on bats, and not the ba ts on me! I also in tend, during the course of this lecture to show that all I do and know about in Zoology is not just bats.
Open Access
The Influence of Geological Factors on the Engineering Properties of some Western Nigerian Residual Lateritic Soils as Highway Construction Material.
(Obafemi Awolowo University, 1985) Mesida, Ebenezer Ajibola; Akinmusuru, Joe
The fundamental influence of geology on some geotechnical properties of lateritic soils as highway -construction material within a restricted macroclimatic area of Akure and llesha in the deciduous rain forest belt of South Western Nigeria was investigated. Lateritic soils derived from four major petrological units, namely t'.aarse, P~yrphyrit.ie Granite, Coarse to medium Charnockite, Coarse to medium massive amphibolite, and medium Grained Talc Schist were concentrated upon the different ways in which Geochemistry, Clay Mineralogy, Degree of weathering and Laterization influenced the engineering properties of the sails were examined. The results have conclusively proved that geology is the main factor controlling the geotechnical properties of residual lateritic soils within the restricted climatic environment. A new parameter, termed the water absorption coefficient of lateritic soils was evolved. It is the angular relationship between the 48-hour soaked CBR value of a soil and average percent value of the soils' CBR at Optimum Moisture Content of Modified AASHO acompaction. The mean values of the coefficient in the four soils studied showed discernible relationship to the respective parent rocks. Recommendations for further research include an investigation of the relationship between the shear strength parameters of compacted genetic lateritic soils especially in the triaxial test: and the relationship between the water absorption coefficient and the geophysical resistivity values of similarly compacted genetic lateritic soils. Such subsequent research may eventually provide convenient quantitative engineering parameters which would relate the variations of moisture content, dry density, geophysical resistivity and the triaxial shear strength values in genetic lateritic soils in general.
Open Access
Chemical Examination of the Leaves of AZADIRACHTA INDICA A. JUSS. (NEEM) for Insect Anti-Feedants.
(Obafemi Awolowo University, 1985) Adesanya, Adepeju Olubamwo; Ogunkoya, L.
The chemistry of the extractives from the leaves of Azadirachta indica and its closely related species, Melia azedarach is reviewed. Cold methylated spirit was resolved into four fractions on the basis of their solubilities in the non-polar solvent hexane and in aqueous alkali. Each of these fractions was tested for repellent activity on the bean seed weevil; Callosobruchus maculatus. three of the fractions inhibited the emergence of the bean seed weevils and were therefore considered to possess the expected insect repellent activity. From one of these fractions, thick oil was isolated after purification using idolumn and thin layer chromatographic methods. Spectroscopic studies of this thick oil revealed the presence of one major compound whose molecule contained an ester group and a C=C in conjugation with another Pi electron system.
Open Access
Guinea Savanna Structure and Land-use in Northwestern Nigeria.
(Obafemi Awolowo University, 1985) Ero, Isaac Izogie; Sanford, W. W.
The Guinea savanna of northwestern Nigeria was characterised using parameters of climate, soil and vegetation. The scale of variability of the attributes measured in the four localities - Yelwa, Mokwa, Borgu and Jebba - was assessed and found in the case of soil and vegetation to be significant on at least a hectare to hectare scale. Density of all species, the most abundant species, size class distribution, and pattern of woody elements were estimated. Principal component analysis was employed to explore the correlation and variability of soil attributes (sand, silt, clay, organic carbon) and vegetation characteristics between plots and localities. Broad homogeneity in edaphic features was shown, while marked differences existed between plots in each location. The vegetation was heterogeneous in respect of most physiognomic/structural attributes, although considerable homogeneity was observed at Jebba and some at Mokwa. The relative physiognomic/structural heterogeneity was shown to parallel that of soil attributes and in some cases to be directly related to specific soil attributes. The stability and resilience of the sample plots were assessed. The Markovian prediction model gave varying values of weighted relative change showing that successional or maturity class differences are not mainly dependent upon differences in species composition. High diversity indices are related to stability if log-normal species distribution indicated stability, but if geometric species distribution indicates stability then stability is associated with low diversity. It is concluded that land-use and vegetation mapping must done on a local scale permitting the application of management is to delineated land units. The attributes concerning ability (functional/compositional stability) vary in relation to specific land use and should be accordingly assessed. Recommendations are made for such assessment together with listings of parameters most practical for land-use planning in the Guinea savanna.
Open Access
Ecology and Biology of Piliostigma Thonningii (Schum.) Milne-Redhead in the Guinea Savanna Zone of Nigeria.
(Obafemi Awolowo University, 1985) Mbaekwe, Ebenezer Ike; Isichei, A. O.; Sanford, W. W.
Eighteen plots in selected sites from the Mokwa, Kainji and Yelwa areas of the Nigerian Guinea savanna were sampled systematically for vegetation attributes. Four belt transects in each plot were sampled to estimate the density of all woody individuals greater than 1m high, density of Piliostigma thonningii, total basal area of woody species, and woody plant cover. Soil samples were randomly collected from the 0-15cm depth in the plots and analysed for texture organic matter and nitrogen. The vegetation and soil data and attributes derived from them were used for ordinations using principal components analysis. The ordinations show that soil factors namely sand: clay ratio organic matter and nitrogen content were, in association with some vegetation attributes, important in determining the distribution and density of P. thonningii in the areas studied. Some aspects of the biology of the plant were also studied. Best germination results were obtained after acid treatment. The phenology of the plant and its response to perturbations were observed and these observations gave an insight into its mode of propagation. Anatomical studies showed the leaf characters as being semi-xerophytes and the stem as having growth rings. The age of the plant could be estimated from ring counts. Examination of the plant for nodules did not yield positive results but nitrogen levels in the leaves compared favourably with those of other browse plants in the same area. This identifies the plant as an important browse species in the savanna. Overall, the study has highlighted the conditions under which the plant grows and its rich potential as a source of cover and browse in the Guinea savanna.