ECOLOGICAL MANAGEMENT

          TOPIC:  ECOLOGICAL MANAGEMENT

          Associations Specific Objectives:  By the end of these lessons, the student should be able to:

        a.     define association as a biological term

        b.     State the types of biological associations

        c.      Describe and give examples of each type of association.

                  WHAT ARE Biological Associations?

        By way of illustration the teacher introduces the students to certain associations in everyday life.  He explains that any kind of relationship between 2 or more persons which may be beneficial or harmful to either or both parties is an association.  By way of definition, the teacher defines Biological association as a beneficial harmless or harmful relationship resulting from interaction between or among organisms.

        Since organisms in the ecosystem are constantly interacting with        other organisms and with the physical environment, they need to adjust themselves so as to cope with problems of survival in their environment, the teacher explains that that is the subject of ecological management.  It deals with activities aimed at balancing changes in an ecosystem to bring about optimum survival of organisms.  In order to achieve this, organisms go into various biological associations.

        Types:  There are many types of such associations. These include:

-      Symbiosis

-      Predator – Prey relationship

-       Saprophytism

        Symbiosis is a close association between two or more unrelated organisms which may be beneficial, harmful or neutral.

        3 types of symbiotic associations include:

-      Mutualism

-      Parasitism and,

-      Commensalism

        Mutualism is a symbiotic association between two organisms in   which both of them benefit from each other.  Each member of the association is a symbiont.

        Examples:

        A.      LICHEN:  Symbionts ===>  Algae & Fungus

                Cross Section of a Lichen

          Lichen is a symbiotic association between a fungus and green algae which lives in close association.  The algae are enclosed by the fungus and protects it from physical damage and from desiccation.       It also absorbs some water from the environment used by the algae.  The algae in turn manufactures food by photosynthesis to       feed the fungus.

        B.      PROTOZOA IN THE INTESTINE OF TERMITES

                Termites eat wood but lack cellulose to digest cellulose in the             wood.  However, they have in their gut protozoa of the type                trichonympha which secretes an enzyme that digest the                        cellulose.  The protozoa benefit in the following ways:

        i.      They are provided shelter by the termite

        ii.      They get protection from the termite

        iii.     The termite provides them with cellulose from which they                 digest to get sugar.  The termite gains sugar from the cellulose they feed on.

        C.      NITROGEN FIXING BACTERIA IN THE ROOTS OF                            LEGUMINOUS PLANTS

                A bacterium called Rhizobium leguminosarium lives in the                 root nodules of leguminous plants, obtain nutrients from the             cells of the host plants, grow and multiply or reproduce there.            In turn, the Rhizobium gives nitrogen directly into the plants         from the atmosphere thereby increasing the nitrogen                       availability of legumes.

        D.      BACTERIA IN THE GUT OF HERBIVORES

                   Certain cellulose bacteria inhabit the rumen of herbivores like cattle, goat and sheep etc.  They are able to digest cellulose using their self produced cellulose. They therefore provide a wide range of sugars for the plants while they in turn get shelter, protection, food and minerals from the plants.

          E.      FLOWERS AND INSECTS

                   Insects obtain food from plants in the form of pollen and nectar while in turn they pollinate the plants enabling them         to undergo sexual reproduction.

        F.      MYCORRHIZA

                   There are two types:  Endo/cotomycorrhiza.

                This is an association between a fungus and the roots of higher plants. The fungi act as root hairs and aid in transferring inorganic nutrients from the soil into the plants. The plants supply the fungus with organic nutrients.

        G.      CATTLE AND EGNETS (TICK BIRDS)

                   Cattles are groomed by tick birds which remove blood sucking glues and ticks from their bodies.  In this association, the birds get food by eating the ticks while the cattle benefit by having their parasites infestation reduced.  This enables the cattle to thrive and be more productive.

        Commensalism:  This is a symbiotic association of two different       organisms in which one (the commensal) derives some benefits   while the other (host) neither gains nor suffers harm.  The         advantages involve shelter, support, food or combination of factors.      A typical example is between the shark and the little manne fish        called Remora.  The remora’s dorsal fin is modified into a hold fast-     like structure.  By means of this the remora attaches itself    temporarily to the underside of a shark.

he remora eats the scraps of food falling off when the shark feeds.  The remora gets protection from predators and a wide distribution, the shark, however, is not affected by this association.

Many gut bacteria are commensals especially in the large intestine.    They feed on the unwanted waste and get protection while at       normal flora we are unaffected.

Epiphytes and Trees:  Epiphytes are sun loving plants that climb       and grow on trees to be adequately exposed to the sunlight.  The         trees provide a base for attachment and position for them while the      tree is either harmed or benefited.  Example is Platycerum and tall      trees.

Hermit Crab and Hydrachatine:  Hermit crabs house and convey    a type of hydra called hydrachatine in its shell.

        The hydrachtine feeds on the food particles obtained from the crab    which gains nothing from the association

PARASITISM

          This is an association involving a parasite and a host.  The parasite     lives and derives nutrients and protection from the host while the    host suffers serious harm from the parasite.  Parasites include      viruses, bacteria, protozoa, fungi and invertebrates like round        worms and platyhelminths and some arthrodopa, some flowring         plants like stinga (witch weeed, and dodder (euscuta).

        Parasites may be

·         Endoparasites or

·         Ectoparasite

        Endoparasites live inside the body tissues of their host and sap   them of the nutrients resources and may cause death to their host.     Examples melinde – Tapeworm, Hook worm, trypanosome, plasmodium, liverfluke etc. 

        Ectoparasites are those parasites that live outside the body of their     host.  They attach to the surfaces of the host’s body with special        structures for attachment eg, lice, ticks, fleas.

        A parasite passes most of its life in/on the body of its host.

        Benefits to parasites – food – shelters – protection

        Effect Of Parasitic Action ON The Host

        Parasites do not always kill their host except certain parasites called   Parasitids. Parasites damage the host’s tissues – they produce toxins inside their host.  These toxins may cause disease or poor   health.  Many ectoparasites act as vectors e.g tick spread babesia and rat fleas spread the plague causing bacteria.

        Effects include stunted growth, tiredness, lack of resistance to   disease, low productivity.

        Diseases caused by parasites include:

-      Black pod disease of cocoa caused by fungus phythopthora parmivora

-      Blast, rust and smut of cereals by fungi

-      Gonorrhea, Tuberculosis and leprosy by bacteria

-      Babesiosis by protozoa

ADAPTATIONS OF PARASITES

-      Possession of organs for piercing the host body surface and sucking

-      Presence of specialized boring organs

-      Presence of attachment structures eg, ectoparasites

-      Ability to secrete enzyme capable of dissolving tissues

-      Presence of good reproductive means

        Some Important parasitic plants include:

        Dodder (cuscuta) + Mestletoe (Tiponanthus lorantnus)

        Special Features:   Attachment structures eg, hook claws and suckers

ü  Flat body shape for non-easy brush off from the host

ü  Piercing and sucking mouth parts for feeding

ü  Ability to produce anticoagulant to prevent blood dottings.

        ENDOPARASITES

          Special Features

-           Poor digestive system ==> Organs of movement and sense organ

-           Hermaphrodites

-           Lays large number of eggs produced to increase chances of infesting new hosts

-           Complicated life cycle involving 2 hosts

-           Production of anti-enzymes to neutralize host’s enzyme

-           Ability to respire in low oxygen supply

-           Presence of attachment structures and suckers

        Important endoparasites include (Humans)

·          Tapeworm

·          Hookworm  

·          Pin worms

·          Ascaries (round WORM)

·          Threadworms

·          Filaria worms etc.

TAPE WORM

          These are long parasitic worms which live in the gut of humans.  Several species exist but paramount are the

-      Cattle tapeworm -à Taenia Saginatta

-      Pig tapeworm  --à  Taenia Solium

        Adaptive Structures

          Include and specific from the general features mentioned above are

v  Flat tape – like bodies for easy diffusion and movement

v  Small spherical head bearing (scolax)

v  Suckers for absorption of nutrient from host

v  Large number of egg bearing proglottides

v  Hooks for attachment to the intestinal wall of host.

Internally the worm is simplified as a result of adaption to its parasitic way of life.  No mouth or well developed alimentary canal.  It therefore absorbs food digested by its host over its body surface.  No organs of circulation nor respiration.  Its excretory organ is the flame cell.  Tapeworms are hermaphrodites

        Life Cycle:  Two hosts are involved in the life cycle viz: 

        a.     Human host as primary host and another animal (cow of pig)     as secondary host.  The proglottids at the posterior end mature and breaks off being filled with eggs are passed out in   human faeces. This develops into the embryo with 6 hooks covered with a protective shell.

        If the eggs are eaten by a foraging pig or grazing cattle, the embryo is swallowed and is released from a protective shell by the action of digestive enzyme produced by the secondary host.  The embryos burrow into the bloodstream through the walls of the intestine.  They are carried by the blood and loosed in the insiders where they stay and develop.  They now grow into a cyst and latter into a bladder.  Part of the bladder forms a proscolax resembling the head of a tape worm turned inside out.  This is called a bladderworm.  If undercooked pork or beef is injected by humans the bladerworm is introduced into the intestine of the human where it develop into a new tapeworm.

Life Cycle of Tapeworm

Economic Importance

v  Tapeworm do not cause any severe symptoms since their presence in the body is unnoticed if not in stool, but since they rely on digested food they can cause anaemia.

v  They lower the body’s resistance to disease

v  They cause irritation of the intestinal wall which cause abdominal pain

v  It causes ulcer of the intestinal wall

v  They cause loss of appetite, vomiting and loss of weight or emaciation, nervous disorder and indigestion.

           

            Control of Tapeworm

v  Proper sanitation ensures that eggs do not contaminate food – Pork/beef should be examined by veterinary doctors before killing

v  Well cooked meat

v  Proper treatment of infestation should be observed.

            Evaluation:  To be drawn from page 178 – 180 of ……………………… Biology

                Home work:

          1.     Describe the life cycle of any 2 ectoparasite and

        2.     State the economic importance of mosquito in the world

        Reading Assignment:  Read on Tolerance & Ectoparasites