Amoeba Euglena Paramecium Structure Mode of life Economic

Amoeba, Euglena, Paramecium. Structure Mode of life Economic Importance Ande A. T and Omoyayi I. O (NYSC)

Euglena Introduction • shows a mixture of plant and animal features • are protozoans in the phylum: Sarcomastigophora subphylum: Mastigophora • inhabits slow moving fresh water ponds lakes that are rich in organic matter and not turbid • Their green colour imposes a green colouration on the aquatic medium they dwell in • A common example is Euglena viridis

Euglena • • • Structure They have a constant shape which is spindle Length varies between 30 and 3000 mm They are unicellular or acellular The cell is the eukaryotic type The body wall is composed of a cell membrane, a pellicle within that maintains its shape and thickened longitudinal stripes and myofibrils (Myonemes) At the swollen end is a reservoir lined by the cell membrane only and with a narrow neck - gullet In the reservoir are two flagella (long and short), photoreceptor, stigma Within the protoplasm are a nucleus, nucleolus, chloroplast, pyrenoids, contractile vacuole etc They are asymmetrical

Euglena

Mode of life • Movement ü They employ the myonemes and long flagellum in euglenoid and flegella movements respectively • Nutrition ü They are capable of feeding autotrophically, heterotrophically and saprophytically • Respiration ü Exchange gases by diffusion across the body wall

Mode of life cont’d • Circulation ü By diffusion and protoplasmic streaming • Excretion and Osmoregulation ü They utilize the contractile vacuole that are specifically located next to the reservoir • Irritability ü They use the combination of stigma and photoreceptor to locate light for photosynthesis • Reproduction ü Asexual method only and this is by longitudinal binary fission

Amoeba Introduction • They show animal features • They are protozoans in the phylum: Sarcomastigophora subphylum: Sarcordina • They inhabit stagnant fresh water ponds lakes that are rich in organic matter • They dwell at the bottom of the water amidst sediments • A common example is Amoeba proteus

Amoeba • • • Structure They do not have a constant shape as they lack pellicle They have a slightly viscous gel-like ectoplasm to bestow shape Diameter of 0. 1 mm They are unicellular or acellular The cell is the eukaryotic type its body wall is composed of cell membrane only The cytoplasm is composed of ectoplasm and endoplasm that are inter convertible The ectoplasm is outer, viscous, plasma gelled and lack granules hence it is clear while the endoplasm is granular the endoplasm contains nucleus, fat droplets, food vacuoles, excretory materials, and all these have no constant position within the cytoplasm They are therefore basically assymmetrical

Mode of life • Movement ü They employ their constantly changing shape informed by the pseudopodia formation • Nutrition ü They feed heterotrophically ü They consume diatoms rotifers and minute particles in water debris ü These are ingested by phagocytosis to form food vacuole. Digestion takes place in the vacuole, absorption of digested food occurs by micropinocytosis and egestion of undigested food is ensured by exocytosis at any point on the body wall • Respiration ü Exchange gases by diffusion across the body wall

Amoeba - Locomotion 1. Ectoplasm extends and the endoplasm flows in, forming a pseudopodium. 2. Pseudopodium continues to extend and the endoplasm continues to flow so that the whole amoeba is moving to the right. 3. A new pseudopodium starts to form 4. The endoplasm flows into this. 5. As a result, the amoeba has changed its direction of movement

Engulfing its prey

• Video of Amoeba feeding

Breathing - gaseous exchange by simple diffusion oxygen maximum distance for diffusion is about 0. 1 mm carbon dioxide Because amoeba is so small, the surface area of its cell membrane is very large compared with the small volume of its cytoplasm. The demands of the respiratory processes in the cytoplasm can therefore be met by the diffusion of oxygen and carbon dioxide between the cytoplasm and the surrounding water. Oxygen diffuses in and carbon dioxide diffuses out.

Mode of life cont’d • Circulation ü By diffusion and protoplasmic streaming • Excretion and Osmoregulation ü They utilize the contractile vacuole that form anywhere on in the body and throws out an any part of the body wall • Irritability ü They use the cell membrane as their sense organ and this is sensitive o chemical stimuli • Reproduction ü Asexual method only

Reproduction – Binary Fission 1. Stops moving and rounds off 2. The nucleus begins to divide. 3. The nucleus has divided and the cytoplasm starts to constrict. 4 & 5 The constriction continues to divide the cytoplasm. 6. The daughter amoebae separate.

Paramecium Introduction • Shows animal features only • are protozoans in the phylum: Ciliophora • inhabits stagnant or slow moving fresh water rich in decaying organic matter • Demonstrates very high degree of cellular differentiation because it has complex organelles designed to perform specific functions • Its is therefore regarded as a complex protozoan • A common example is Paramecium caudatum

Paramecium Structure • They are unicellular or acellular • The cell is the eukaryotic type • They have a constant shape with blunt anterior and tapering posterior ends. Having the look of a slippers hence they are described as slipper animacules • The shape is maintained by a rigid pellicle which is strong and flexible

Paramecium structure continued • The body wall is formed from an outer cell membrane pellicle and an inner ectoplasm with firm plasma gel • Paramecium is covered by cilia that are arranged in longitudinal rows • Within the body wall are flask shaped trichocysts that serve for anchorage • Midway between the anterior and posterior end is the oral groove which is a depression with special cilia known as undulating membrane for ingestion of food

Paramecium - Structure

Paramecium structure continued • The oral groove leads to the bucal cavity or gullet and to the cytopharynx at the end of which is the cytostome with naked endoplasm • Also on the body wall is an opening for throwing out undigested waste products known as anal pore or cytoproct • Also in the endoplasm are two nuclei, i. e macronucleus and micronucleus food vacuoles anterior and posterior contractile vacuoles, lysosomes, etc

Paramecium - Locomotion • Propels itself by beating the cilia with a power and recovery stroke • Paramecium moves slowly and gently • When obstructed, it slowly reverse, make a slight turn, and continue its slow cilia movement.

Mode of life cont’d • Nutrition ü They feed heterotrophically ü They consume suspended organic particles the undulatingmembranes beat to encourage ingestion of the particles into the oral groove and finaly ato the cytostome ü At the cytostome food particle and some water form a food vacuole ü The food vacuole then moves around in the endoplasm during which digestion and absorption of digested food occurs and

Paramecium - Feeding circuit followed by food vacuoles food particles drawn into oral groove by ciliary current food ingested into a food vacuole undigested remains expelled

• Video Lecture of Paramecium eating pigmented yeast.

Mode of life cont’d • Respiration ü Exchange gases by diffusion across the body wall • Circulation ü By diffusion and protoplasmic streaming • Excretion and Osmoregulation ü They utilize the contractile vacuole that are specifically located at the anterior and posterior part of the cell

Mode of life cont’d • Irritability ü They use cilia and body wall. They are sensitive to chemicals, oxygen and carbon IV oxide • Reproduction ü They reproduce asexually and sexually ü Asexual method is by transverse binary fission ü Sexual is by conjugation

Paramecium - Reproduction • Reproduction by binary fission

Sexual reproduction ü Conjugation entails the exchange of genetic materials and not gametes ü The pellicles of two conjugants dissolve and they fuse at point of contact ü Macro nucleus of each disintegrate ü Micronucleus divide repeatedly. ü Three of each four disintegrate. The one left divides into two – a stationary and a migratory nucleus

Sexual reproduction cont’d ü The migratory are exchanged between the conjugants and the fuse with the stationary to form a zygotic nucleus ü The cojugants seperate ü The zygotic nucleus divides to give four each of macronucleus and micronucleus ü A pair each then moves in each of the four paramecia formed from each conjugant

Economic importance of protozoans. • They help in improving oxygen quality of water bodies • They also help purify water by feeding on organic waste substances in polluted water. • They are very important food for consumers in the aquatic ecosystems • Some of them cause human diseases such as malaria.

General features of protozoans and implications • They are unicellular and limited to water ADVANTAGES DISADVANTAGES Cell is Independent and coordination is better Limited in size and Incapable of differentiating Low food requirement Incapable of specialization Low waste generation High risk of survival High surface area volume ratio Restriction to water • Thus new and more promising organisms in terms of survival and colonizing new habitats must be evolved • the only plausible solution is for the organisms to be MULTICELLULAR

Multicellular arrangement • This is when the animal is made up of two or more cells • These cells require to function essentially as one organism hence there must be coordination between the cells • The advantages of unicellulariity therefore becomes the disadvantages of these type of animals while the discdvantages become advantages

Multicellular arrangement cont’d • The advantages and disadvantages include: ADVANTAGES DISADVANTAGES Size is unlimited and differentiation is possible Cells are not Independent and coordination is required Specialization is now possible hence different forms can be developed High food requirement Low risk of survival hence the animals can survive harsh situations High waste generation Such animals are no longer restricted to water and may even colonize land Low surface area volume ratio

Multicellular arrangement cont’d • Since the addition of cells is gradual is done in an orderly way • The aim is to allow all cells have contact with their environment and enjoy some surface area • The order recognized by way of germ layers are üDiploblastic üTriploblastic Acoelomate üTriploblastic pseudocoelomate üTriploblastic coelomate

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