ADESEMOYE ABIMBOLA CALEB
MBBS (MEDICINE AND SURGERY
BIO 101
SOLUTION TO BOTH ASSIGNMENTS ON LMS
15/MHS01/008
ASSIGNMENT 1
1) a. What is a cell?
Ans: A cell is the functional and structural unit of life. It is the basic unit that constitutes
every living organism and also contain genetic coding that determines the characteristics of
that organism. Some living organisms are unicellular (made up of just one cell) while others
are multicellular (made up of two or more cells).
1) b. Give the features that a true cell should possess.
Ans: Nucleus, Golgi bodies/Golgi apparatus, cell vacuole, Cell wall, Cell membrane,
Protoplasm (i.e. Cytoplasm, cell membrane), Mitochondria, Rough endoplasmic reticulum,
Smooth endoplasmic reticulum, Starch granules, Plastids(e.g. chloroplast), Nuclear
membrane, Nucleolus, Food vacuole.
2). Differentiate between Prokaryotic cell and eukaryotic cell.
Ans: Prokaryotic cell are also known as false cells which have no true nucleus and therefore
is not fully developed WHILE a Eukaryotic cell is also called a TRUE CELL which
possesses a true nucleus and cell membrane/cell wall. It is fully developed.
3). With the aid of well labelled diagrams illustrate the ULTRASTRUCTURES of plant and
animal cells.
4). Briefly describe the structures and functions of the following cellular organelles
illustrating with diagrams where necessary
(a). Nucleus: The nucleus is a an oval structure located fairly at the center of the cell. It is
enclosed by a nuclear envelope to regulate the substances going out and coming in. This
nuclear envelope consists of nuclear pores. Within the nucleus consists genetic material in the
form of chromosomes which consists of genes that carry the genetic information of an
organism for genetic coding of that organism as evident in the physical characteristics of the
organism. The animal cell nucleus contains another oval structure called the nucleolus
(b). Endoplasmic reticulum(EPR): The endoplasmic reticulum is a thick lengthened structure
that forms a network round the entire cell mostly found around the nucleus for moving
proteins round the cell. There are two types of EPR namely: Rough endoplasmic reticulum
and the smooth endoplasmic reticulum. The rough endoplasmic reticulum are the type that
mostly surround the nucleus. They contain protein structures called ribosomes and the genetic
information and coding for making these protein structures are gotten from the nucleus.
(c). Mitochondria: The mitochondrion is a bean, sometimes oval shaped organelle which is
responsible for energy (heat) production within the cell. It is also called the power house of
the cell. It contains an irregularly shaped mass called CRISTAE.
(d). Golgi apparatus: The Golgi apparatus is sometimes called Golgi body. It structure takes
the form of flattened plate like substances stacked on top of each other. The function in
transporting substances within the cell and also in transporting waste substances outside the
cell. It does this by breaking of at its ends to form a small vacuole. These small vacuoles
contain the substances to be transported.
(e). Plasma membrane: The plasma membrane also known as the cell membrane is a living,
thin sheet covering the whole cell. It allows only some selected PARTICLES to pass through
on the basis of their size and on the concentration gradient between the cell fluid and the
surrounding fluid. It is present in both plant and animal cells. In plant cells it is overlapped by
a non-living, permeable cell wall.
(f). Cilia and flagella: These a locomotory structures which enable locomotion of the
organism in most cases and in other cases is for the movement of other substances, e.g. food
substances. The cilia are shortened hair like structures that cause locomotion by beating while
the flagella are flattened and longer structures which also cause locomotion by beating. Both
could be found in both lower and higher organisms.
5). How can you differentiate between cilia and flagella?
Ans: Cilia are shortened hair like structures that cause locomotion by beating WHILE the
flagella are flattened, thread like and longer structures which also cause locomotion by
beating. Both could be found in both lower and higher organisms.
6). Explain symbiosis, commensalism and protocooperation as positive forms of biologiacal
interactions giving examples where necessary.
Ans: (a). Symbiosis is also called symbiotic nutrition. It is a mode of nutrition by which
two organisms benefit mutually from their association. The two organisms benefit from
themselves e.g. Shark and the remora fish. The shark benefit from the remora fish when it
cleans the sharks body by eating off the dirt while the remora fish benefits protection from
the shark because other fish are no match for the shark in a fight.
(b). Commensalism is a mode of nutrition in which two organisms are involved but only
one of the two organisms benefit from the association. It is different from parasitism in that
one organism looses and the other gains. In commensalism one organism gains but the other
doesn’t lose neither does it gain.
(c). Protocooperation is where two species interact with each other beneficially; they
have no need to interact with each other - they interact purely for the gain that they receive
from doing this. It is not at all necessary for protocooperation to occur; growth and survival is
possible in the absence of the interaction. The interaction that occurs can be between different
kingdoms. Protocooperation is a form of mutualism, but they do not depend on each other for
survival. An example of protocooperation happens between soil bacteria or fungi, and the
plants that occur growing in the soil. None of the species rely on the relationship for survival,
but all of the fungi, bacteria and higher plants take part in shaping soil composition and
fertility. Soil bacteria and fungi interrelate with each other, forming nutrients essential to the
plants survival. The plants obtain nutrients from root nodules and decomposing organic
substance. Plants benefit by getting essential mineral nutrients and carbon dioxide.
7). Explain exploitation, predation and amensalism as negative forms of biological
interactions citing examples where necessary.
Ans:
(a). Exploitation/Cheating is commonly used in behavioural ecology to describe organisms
that receive a benefit at the cost of other organisms. Exploitation is common in many
mutualistic and altruistic relationships. An exploiter is an individual who does not cooperate
(or cooperates less than their fair share) but can potentially gain the benefit from others
cooperating. Exploiters are also those who selfishly use common resources to maximize their
individual fitness at the expense of a group. Natural favours cheating/exploitation, but there
are mechanisms to regulate cheating.
(b). Predation: In ecosystem predation is a biological interaction where a predator (an
organism that is hunting) feeds on its prey (the organism that is attacked). Predators may or
may not kill their prey prior to feeding on them, but the act of predation often results in the
death of its prey and the eventual absorption of the prey's tissue through consumption. Thus
predation is often, though not always, carnivory. Other categories of consumption are
herbivory (eating parts of plants), mycophagy (eating parts of fungi) and detritivory, the
consumption of dead organic material (detritus).
(c). Amensalism is an interaction where an organism inflicts harm to another organism
without any costs or benefits received by itself. A clear case of amensalism is where sheep or
cattle trample grass. Whilst the presence of the grass causes negligible detrimental effects to
the animal's hoof, the grass suffers from being crushed. Amensalism is often used to describe
strongly asymmetrical competitive interactions, such as has been observed between the
Spanish ibex and weevils of the genus Timarcha which feed upon the same type of shrub.
Whilst the presence of the weevil has almost no influence on food availability, the presence
of ibex has an enormous detrimental effect on weevil numbers, as they consume significant
quantities of plant matter and incidentally ingest the weevils upon it.
8)a. An ecosystem is a community of living organisms in conjunction with the non-living
components of their environment (things like air, water and mineral soil), interacting as a
system. These biotic and abiotic components are regarded as linked together through nutrient
cycles and energy flows. It is the relationship between the abiotic components and the biotic
components of the ecosystem (termed 'holocoenosis'). As ecosystems are defined by the
network of interactions among organisms, and between organisms and their environment,
they can be of any size but usually encompass specific, limited spaces
(b). Classify ecosystems citing examples of each type.
(1).Terrestrial ecosystems
Terrestrial ecosystems can be found anywhere apart from heavily saturated places. They are
broadly classed into:
(a). The Forest Ecosystems
They are the ecosystems in which an abundance of flora, or plants, is seen so they have a big
number of organisms which live in relatively small space. Therefore, in forest ecosystems the
density of living organisms is quite high. A small change in this ecosystem could affect the
whole balance, effectively bringing down the whole ecosystem. You could see a fantastic
diversity in the fauna of the ecosystems, too. They are further divided into:
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Tropical evergreen forest: These are tropical forests that receive a mean rainfall of 80
for every 400 inches annually. The forests are characterised by dense vegetation
which comprises tall trees at different heights. Each level is shelter to different types
of animals.
Tropical deciduous forest: There, shrubs and dense bushes rule along with a broad
selection of trees. The type of forest is found in quite a few parts of the world while a
large variety of fauna and flora are found there.
Temperate evergreen forest: Those have quite a few number of trees as mosses and
ferns make up for them. Trees have developed spiked leaves in order to minimize
transpiration.
Temperate deciduous forest: The forest is located in the moist temperate places that
have sufficient rainfall. Summers and winters are clearly defined and the trees shed
the leaves during the winter months.
Taiga: Situated just before the arctic regions, the taiga is defined by evergreen
conifers. As the temperature is below zero for almost half a year, the remainder of the
months, it buzzes with migratory birds and insects.
(b). The Desert Ecosystem
Desert ecosystems are located in regions that receive an annual rainfall less than 25. They
occupy about 17 percent of all the land on our planet. Due to the extremely high temperature,
low water availability and intense sunlight, fauna and flora are scarce and poorly developed.
The vegetation is mainly shrubs, bushes, few grasses and rare trees. The stems and leaves of
the plants are modified in order to conserve water as much as possible. The best known desert
ones are the succulents such as the spiny leaved cacti. The animal organisms include insects,
birds, camels, reptiles all of which are adapted to the desert (xeric) conditions.
(c). The Grassland Ecosystem
Grasslands are located in both the tropical and temperate regions of the world though the
ecosystems vary slightly. The area mainly comprises grasses with a little number of trees and
shrubs. The main vegetation includes grasses, plants and legumes that belong to the
composite family. A lot of grazing animals, insectivores and herbivores inhabit the
grasslands. The two main kinds of grasslands ecosystems are:
1. Savanna: The tropical grasslands are dry seasonally and have few individual trees.
They support a large number of predators and grazers.
2. Prairies: It is temperate grassland, completely devoid of large shrubs and trees.
Prairies could be categorized as mixed grass, tall grass and short grass prairies.
(d). The Mountain Ecosystem
Mountain land provides a scattered and diverse array of habitats where a large number of
animals and plants can be found. At the higher altitudes, the harsh environmental conditions
normally prevail, and only the treeless alpine vegetation can survive. The animals that live
there have thick fur coats for prevention from cold and hibernation in the winter months.
Lower slopes are commonly covered with coniferous forests.
(2). Aquatic Ecosystems
The aquatic ecosystem is the ecosystem found in a body of water. It encompasses aquatic
flora, fauna and water properties, as well. There are two main types of aquatic ecosystem Marine and Freshwater.
(3). The Marine Ecosystem
Marine ecosystems are the biggest ecosystems, which cover around 71% of Earth's surface
and contain 97% of out planet's water. Water in Marine ecosystems features in high amounts
minerals and salts dissolved in them. The different divisions of the marine ecosystem are:
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Oceanic: A relatively shallow part of oceans which lies on the continental shelf.
Profundal: deep or Bottom water.
Benthic Bottom substrates.
Inter-tidal: The place between low and high tides.
Estuaries
Coral reefs
Salt marshes
Hydrothermal vents where chemosynthetic bacteria make up the food base.
Many kinds of organisms live in marine ecosystems: the brown algae, corals, cephalopods,
echinoderms, dinoflagellates and sharks.
(4). The Freshwater Ecosystem
Contrary to the Marine ecosystems, the freshwater ecosystem covers only 0.8% of Earth's
surface and contains 0.009% of the total water. Three basic kinds of freshwater ecosystems
exist:
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Lentic: Slow-moving or till water like pools, lakes or ponds.
Lotic: Fast-moving water such as streams and rivers.
Wetlands: Places in which the soil is inundated or saturated for some lengthy period
of time.
The ecosystems are habitats to reptiles, amphibians and around 41% of the world’s fish
species. The faster moving turbulent waters typically contain a greater concentrations of
dissolved oxygen, supporting greater biodiversity than slow moving waters in pools.
(9)I. (a). Ecological pyramid: An ecological pyramid (also trophic pyramid, eltonian
pyramid, energy pyramid, or sometimes food pyramid) is a graphical representation designed
to show the biomass or bio productivity at each trophic level in a given ecosystem.
(b). Ecological niche: The ecological niche describes how an organism or population
responds to the distribution of resources and competitors (for example, by growing when
resources are abundant, and when predators, parasites and pathogens are scarce) and how it in
turn alters those same factors (for example, limiting access to resources by other organisms,
acting as a food source for predators and a consumer of prey).
(c). Food web: A food web (or food cycle) is the natural interconnection of food chains and
generally a graphical representation (usually an image) of what-eats-what in an ecological
community. Another name for food web is a consumer-resource system.
(d). Food chain: Food chain in a Swedish lake. Osprey feed on northern pike, which in turn
feed on perch which eat bleak that feed on freshwater shrimp.
(9)II. A FOOD CHAIN is a linear network of links in a food web starting from producer
organisms (such as grass or trees which use radiation from the sun to make their food) and
ending at apex predator species (like grizzly bears or killer whales), detrivores (like
earthworms or woodlice), or decomposer species (such as fungi or bacteria)
10). ORDINARY FOOD CHAIN is also called a grazing food chain and it occurs amongst
macro-organisms. This type of food chain starts from the living green plants goes to grazing
herbivores, and on to carnivores. Ecosystems with such type of food chain are directly
dependent on an influx of solar radiation. This type of chain thus depends on autotrophic
energy capture and the movement of this captured energy to herbivores. Most of the
ecosystems in nature follow this type of food chain.
The phytoplanktons →zooplanktons →Fish sequence or the grasses →rabbit →Fox
sequences are the examples, of grazing food chain. WHILE
DEBRRITUS FOOD
CHAIN occurs in the soil or dead decaying organic matter amongst micro-organisms. This
type of food chain goes from dead organic matter into microorganisms and then to organisms
feeding on detritus (detrivores) and their predators. Such ecosystems are thus less dependent
on direct solar energy. These depend chiefly on the influx of organic matter produced in
another system. For example, such type of food chain operates in the decomposing
accumulated litter in a temperate forest.
ASSIGNMENT 2
An organism has 56 chromosomes in its diploid stage. Indicate how many chromosomes are
present in the following, and explain your reasoning.
a). somatic cells: 56 chromosomes will be present in the somatic cells because somatic
cells(body cells) always divide to give daughter cells which are identical to them which
means that these daughter cells will also have diploid number of chromosomes which is also
56
b). metaphase (mitosis): 56 chromosomes are present here because the chromatin threads
just thicken and align along the equator of the cell in metaphase stage and divide into sister
chromatids. The cell is still diploid
c). metaphase I (meiosis): 56 chromosomes; after meiosis I metaphase chromosome
number is still diploid and hence reproductive cell will have 56 chromosomes because both
members of a homolog pair are dragged apart to form a new cell.
d). metaphase II (meiosis): 28 chromosomes; a reproductive cell will have only haploid
number of chromosomes after metaphase II of metaphase because each member of a homolog
pair is dragged apart to form a separate cell.
e). gametes: In gametes there are 28 chromosomes because all gametes have haploid
number of gametes due to the cell division be meiosis after meiosis II.