Animals - Lecture 4 - Sept 19 2013 - POST-2.pdf

8/14/2019 Animals - Lecture 4 - Sept 19 2013 - POST-2.pdf

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OUTLINE

Protozoan Groups

Animal Diversity 6th Ed.Chapter 5, Pages 95 - 117

Animal Diversity 5th

Ed.Chapter 5, Pages 89 - 111

1. Introduction (Classification)

2. Locomotion

3. Nutrition, Digestion &

Excretion

4. Osmoregulation

5. Reproduction


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1. Power Stroke 2. Recovery Stroke

Direction of Organism Motion

CILIARY LOCOMOTION

e.g. Butterfly Stroke

Power Stroke

Recovery Stroke

Direction of Girl Swimming


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Tetrahymena vorax

Normal phase, in the presence of bacteria andother small food items microstome form

[Gk.mikros, small;stoma, mouth]

In the presence of T. thermophila, predatory

phase macrostome form

- Body shape remodeled in response to

T. thermophila presence grows 2x as long

- T. vorax switched from non-selective feeding

to highly selective feeding (on T. thermophila)

cytostome (cell mouth)

Size = 60 m x 20 m

Size = 120 m x 80 m

Examples of Interesting Feeding Mechanisms


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EXCRETION

Elimination of undigested material within digestive vacuole occursvia fusion with cell surface (i.e. ENDOCYTOSIS in reverse)

EXOCYTOSIS

Metabolic wastes- e.g. end products of nitrogen metabolism,

such as ammonia, readily diffuses across cell membrane

PASSIVE DIFFUSION

Waste material accumulates in a vacuole adjacent to the

cytoproct and is periodically discharged (e.g. in ciliates)

CYTOPROCT - permanent excretory pore


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OSMOREGULATION

Hydromineral balance is regulated by specialized

organelles called contractile vacuoles

- Contractile vacuoles are commonly found in freshwater

protozoa & generally absent in marine/parasitic forms

(i) Freshwater is more dilute than the internal

environment of the protozoa

(ii) Ion loss by diffusion and water uptake by osmosiswould result in dilution of the cytoplasm and eventual

death


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OSMOREGULATION

(1) Proton pump (H+-ATPase) Primary active transport

(2) Bicarbonate (HCO3-) co-transport

(3) Passive water diffusion

(4) Cytoplasmic carbonic anhydrase replenishes H+ & HCO3-

H2O + CO2 H+

+ HCO3-


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OSMOREGULATION

Filling and expulsion rates depend on

- ionic/osmotic gradient

- organism size

&&


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REPRODUCTION

Asexual & Sexual phenomena in Protozoa:

Ciliate Reproduction & Life Cycles:

Animal Diversity 6th Ed. P 102-103

Animal Diversity 5th Ed. P 96

General Reproduction:

Animal Diversity 6th Ed. P 107-108

Figs. 5.17 & 5.18

Animal Diversity 5th Ed. P 103

Figs. 5.18 & 5.19


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- Both Sexual (new genotypes) and Asexual (same genotype)

mechanisms are common.

Asexual Reproduction in Protozoans:

1. Binary Fission: controlled mitotic replication of

chromosomes followed by splitting of an individual into 2

individuals.2. Multiple Fission: nucleus divides many times followed by a

rapid differentiation of the cytoplasm into many individuals

(Foraminifera).

3. Budding: part of the parent individual breaks off and

differentiates to form a new complete individual

(Suctorians).

REPRODUCTION


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Sexual Reproduction in Protozoans:

Conjugation: (Ciliates) exchange of genetic material between 2

individuals during a temporary physical association.

- mating types (only different types unite)

-

sometimes involves pheromones- unpackaged genetic material (no sperm or eggs) exchanged

through mating tube

REPRODUCTION


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OUTLINE

Phylum Porifera - Sponges

Animal Diversity 6th Ed.Chapter 6, Pages 118 - 129

Animal Diversity 5th Ed.

Chapter 6, Pages 112 - 122

1. Introduction

2. Cell types

3. Canal systems

4. Reproduction


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INTRODUCTION

- Sessile multicellular animals with no organs or

true tissues.

- filter feeders: system of canals through

which water is pumped into the body andfood particles collected.

- possess functionally distinct cell types.


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INTRODUCTION

Phylum Porifera

Spicules

Calcarea DemospongiaeHexactinellida

Class

Spongin absent absent may be present

Habitat marine marine, deep seamarine &

freshwater

calcium

carbonate six-rayed not six-rayed

siliceous siliceous


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CELL TYPES

1. Choanocytes

- ovoid cells that line canal systems and chambersExposed end

Embedded end

- exposed end, a collar forming a filtering device

- flagellar motion pulls water through filter


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CELL TYPES

2. Archeocytes

- amoeboid cells move through gelatinousmatrix in sponge.

totipotentChoanocyte

Archeocyte

- receive and digest food particles fromchoanocytes.

- give rise to all other cell types in

Sponge like stem cells


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CELL TYPES

a) Sclerocytes (mineral spicules)

b) Spongocytes (spongin spicules)

c) Collenocytes (collagen spicules)

3. Secretory Cells

- Produce spicules and fibres through secretions

Mineral (calcium) Protein (collagen, spongin)

3 subtypes of secretory cells


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CELL TYPES

4. Pinacocytes

- Form protective lining (pinacoderm) that faces the

external environment.

- Also line some internal canals where choanocytes are not

present.

5. Porocytes

- only found in some sponges (Asconoid)

- form channels in pinacoderm through which water

flows to the inside of the sponge (ostia and incurrent

canals).


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General Arrangement of Cell Types in Sponge Body:

ArchaeocytesPinacocytes

(Pinacoderm)

Mesohyl

(gelatinousmatrix)

Sclerocytes

(mineral spicules)

Porocytes

(Ostium)

CELL TYPES

Choanocytes

Spongocoel


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spongocoel

ostium

osculum

pinacocytes

- excurrent canal

- one & large

- incurrent canal

- many & small- porocyte

- pinacoderm

mesohyl

(Gelatinous matrix)

CANAL SYSTEMS

1. Asconoids- flagellated spongocoels

choanocyte- choanoderm

WATER


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CANAL SYSTEMS

2. Syconoids- flagellated canals

Spongocoel NOT lined with choanocytes

choanocyte

chamber


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CANAL SYSTEMS

3. Leuconoids - flagellated chambers

- most sponges are leuconoid

- usually have more than 1 osculum

Sponge volume 2.4 cm3

Osculum # - 1Dermal ostium # - 940 000

Flagellated chamber # - 29 000 000 !

- no spongocoel

Dermal

ostium


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Porifera: Reproduction

- All sponges reproduce asexually and sexually.

Asexual Reproduction in Sponges:

1. Gemmules:-archaeocytes cluster together inside the sponge

and phagocytose other cells to store nutrients.

- Cells on outer perimeter secrete thick protective

covering of spongin and spicules.

- Cluster of cells and covering = gemmule.

- Gemmule withstands dessication, freezing temp., low oxygen.

- When conditions favourable, archaeocytes leave gemmule through

micropyle (opening in gemmule) and differentiate into new

individual.


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Sexual Reproduction in Sponges:

- Elusive processes because no specific reproductive structures.

- sponges of Demospongiae are most studied.

Viviparous sponges:

- sperm formed from choanocytes and released into the water

- Eggs formed from archaeocytes (sometimes choanocytes), distributed

throughout mesohyl.

Oviparous sponges:

- release egg and sperm to the environment (usually a mass population

event at one time of the year

- fertilization and development all occur in the environment.

- Zygotes develop into a flagellated free-swimming larva - parenchymula



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Oviparous Sponges:Male sponge: sperm release Female sponge: egg release


Animals - Lecture 4 - Sept 19 2013 - POST-2.pdf

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