Movement, Locomotion And Support Flashcards
Give the importance of support in terrestrial plants
- Enables holding leaves to receive maximum sunlight for photosynthesis
- Enables exposing flowers in the most suitable position for pollination
- Allows holding fruits and seeds in the possible favourable position for dispersal
- Maintains plant shape.
Describe the support mechanisms in dicot plants
- Turgidity of cells
Turgor pressure: outward pressure from the inside of a fully turgid cell.
When fully turgid, the close packing of parenchyma cells in cortex and pith of the stem causes them to press against one another to keep herbaceous plants and young woody plants erect. Absence / insufficient water reduces turgor pressure causing loss of support due to wilts. - Mechanical tissues
(a) Collenchyma cells have uneven thickened cellulose cell walls, and are alive.
(i) Collenchyma tissue provide flexible support (a mechanical function) to stems and leaves, enabling withstanding the lateral force of the wind.
(ii) The walls of collenchyma cells can be deformed by pressure or tension and retain the new shape even if the pressure or tension ceases.
Location: in young plants, herbaceous plants and some organs such as leaves
(b) Sclerenchyma fibres and sclereids have lignified cell walls and are dead when mature.
(i) The tough and elastic cell wall of elongated fibres allow the cell to be deformed but can snap back to their original size and shape when the pressure or tension is released.
(ii) Provides great tensile or compressional strength in plants parts, such as in the vascular tissues of stems and roots and the bundle sheath of leaves
(iii) Support the tree while the elasticity allows the trunk and the branches to sway in the wind without breaking. Location: found in small groups in cortex, pith, phloem and shells of coconuts. - Distribution of vascular tissues (xylem vessels and tracheids)
The distribution is related to the resistance of the various forces acting upon them, e.g. in land plants the stem is mainly exposed to bending stresses due to the action of wind while roots experience pulling stress.
(i) Xylem vessels and tracheids are dead, the cell walls are lignified and thickened which provides great mechanical strength to resist bending in the stem, reinforce against pulling in the root and are the most important supporting cells in the veins of leaves.
(ii) Vascular tissue in young dicot stems
Location: at the root periphery (near edge) This increases the resistance to the bending stresses produced by wind or the passing animals.
(iii) Vascular tissue in dicot roots
Location: at the root centre
The solid cylinder increases the tensile strength to resist the uprooting force produced by the pulling effect of wind.
The solid cylinder also provides sufficient incompressibility against the longitudinal compression by the load from overhead and against the lateral pressure exerted by the surrounding soil
(iv) In leaves, vascular tissue is located at the upper side of midrib and lateral veins, and it extends throughout the leaf surface. This enables resisting tearing forces acting on the leaves blade by the wind.
(v) In woody stems, the lignified secondary xylem tissues (known as wood) occupy most part of the woody stem, which makes the stem very hard and rigid to avoid depending on cell turgidity for support
Describe support mechanisms in aquatic plants (hydrophytes)
Support from buoyancy is provided by:
1. Surrounding water, whose density is much higher than that of air, hence providing a larger upthrust force.
2. Presence of numerous large air spaces (intercellular spaces) in stems and leaves, which form air-filled cavities extending through the tissues, inside to give buoyancy.
Why is it that when removed from water, most hydrophytes collapse quickly?
This is because of having poorly developed (some lack) mechanical tissues (i.e. collenchyma and sclerenchyma) and xylem tissue is reduced, since it is unnecessary (no need to transport water within the body and buoyancy is provided by water for support).
Give differences between support in terrestrial plants and that in hydrophytes
Terrestrial Plants
- Require mechanical support because air will not hold up plant structures in the same way that water does.
- The presence of collenchyma cells, sclerenchyma cells and the abundant highly lignified thick-walled xylem vessels in terrestrial plants implies that support depends on these specialized thick-walled cells.
- Small air spaces in stem since air with low density only provides limited support to plants.
Aquatic Plants
- Density of water is much higher than air, hence providing a larger upthrust force
- No collenchyma and sclerenchyma cells are found in aquatic plants, and the poorly developed xylem vessels indicate that aquatic plants do not depend on these cells for mechanical support.
- There are numerous large air spaces in the stem and the leaf of aquatic plants suggest that aquatic plants depend on the buoyancy
Define Locomotion
The act of changing position by the entire body.
Define Movement
The act of displacing body parts while maintaining the whole body in one position.
What is the importance of amoeboid movement to organisms involved?
a) Enables amoeba to move about to
(i) obtain food
(ii) avoid dangers
(iii) escape from energy.
b) Enables white blood cells (Leucocytes) like phagocytes, macrophages of the lymph and Kupffer cells of liver to
(i) engulf antigen or microbes
(ii) immigrate in the circulatory fluid.
What is the importance of ciliary and flagellar movement?
a) Ciliary movement enables paramecium to
(i) avoid danger
(ii) drive water and food into their gullet.
b) In certain molluscs Ciliary movement facilitates gaseous exchange by passing water currents over the gills
c) In echinoderms Ciliary movement enables locomotion by driving water through the water vascular system.
d) Ciliary movement of the cells lining the respiratory tract of humans drives away the microbes and dust particles towards the nose or mouth.
f) Ciliary movement in the oviduct or fallopian tubes of human female moves ova towards the uterus.
g) Ciliary movement in nephridia of annelids e.g. earthworms moves wastes
h) Flagellum of sperms enables their swimming movement.
i) Flagellum enables the movement in certain protozoans like euglena
Describe the importance of muscular movement in organisms involved
Muscular movements enable
(i) animals to find food, mate up, avoid predators and unsuitable environmental conditions
(ii) flow of contents in the gut and arteries
(iii)positioning of eyes and external ears for effective functioning in some animals
What is amoeboid movement?
This is a crawling-like type of movement characterised by protoplasmic protrusion to form temporary feet-like structures called pseudopodia.
What is ciliary movement?
The rhythmic beating of fine hair-like processes projecting from the cell membrane of certain cells (cilia).
Describe ciliary movement
●A ciliary beat cycle consists of an effective (power) stroke phase and a passive recovery stroke phase.
●During the effective stroke phase the fully extended cilium makes an oar-like movement towards one side exerting maximum force on the surrounding fluid. The cilia beat in reverse when the power stroke is directed toward the anterior end of the organism so as to propel it backwards while beating towards the posterior end causes the cell or organism to swim forward.
●In the passive recovery stroke phase which follows the effective stroke, the cilium moves back by propagating a bend from base to tip in an unrolling motion to reduce drag.
●The cycles of adjacent cilia are slightly out of phase so that they do not bend at exactly the same moment, resulting in metachronal rhythm in which waves of ciliary activity pass along the organism from front to rear.
Give the unique properties of muscles which enable their functionality
(a) Excitability
(b) Contractibility
(c) Extensibility
(d) Elasticity Muscular movement is dependent on skeletal systems.
Give examples of organisms in which the Hydrostatic skeleton or Hydroskeleton is found
It’s the most widespread type of skeleton found in:
a) Organisms like annelids (e.g. earthworms), cnidarians (e.g. jellyfish, sea anemones), nematodes (e.g. round worms)
b) Structures like mammalian eyes (the aqueous and vitreous humour), spinal cord (cerebrospinal fluid), extra embryonic membranes (amniotic fluid), hearts (move blood), and intestines (move food).
What is the Hydroskeleton?
This is a high-pressured fluid in a cavity (coelom), surrounded by muscle layers at different orientations.
What is the main principle on which the hydroskeleton operates?
The low compressibility of liquid water (often assumed incompressible).
Muscle contractions exert pressure on the coelomic fluid causing stiffening of the outer structures to form a strong rigid skeletal unit that provides a base against which movements can occur.
What is the effect of too much water loss and too much water gain in hydrostatic skeleton?
Too much loss of fluid causes limpness of tissues and pressure loss, and too much gain causes over swelling, both of which fail muscle stretching and hence movement fails.
This explains why snails and earthworms are restricted in their activity to moist conditions.
Give examples of organisms with the Exoskeleton
●Chitinous exoskeleton is in: arthropods like insects, arachnids (e.g. spiders) crustaceans (e.g. crabs, lobsters), some fungi and bacteria
●Calcified exoskeleton is in: shelled mollusks (e.g. snails, clams), some polychaetes like lugworms.
●Silicated exoskeleton is in diatoms. ●Bone, cartilage, or dentine make up the exoskeletons of turtles and primitive fish
What is an Exoskeleton?
This is a non living external body structure that supports and protects an organism.
What secretes the exoskeleton?
Ectoderm
Give examples of organisms with the Endoskeleton
Found in:
a) Chordates: birds, mammals, reptiles etc.
b) Echinoderms: starfish, brittle stars, sea urchins, sea cucumbers
c) Poriferans: sponges
d) Molluscs (class Cephalopoda) e.g. cuttlefish
Note: Some animals, such as the tortoise, have both an endoskeleton and an exoskeleton.
What is the Endoskeleton?
This is a living internal support structure of an animal, usually composed of mineralized tissue which develops within the skin or in the deeper body tissues.
Give the advantage of the Hydroskeleton
●Hydroskeleton is elastic and can bend accordingly when a muscle contracts enabling fitting in narrow burrows.
Give the disadvantage of the hydroskeleton
● Coelenterates that use a hydroskeleton regularly face a loss of pressure because their skeleton is also their gut.
● Due to lack of a strong supportive system, majority of the invertebrates are small
●The slow motion due to lack of effective ways to support a large body compromises the animals’ escape response from predators.
●The organisms are limited to moist habitats because of the need to minimise water loss by evaporation
What are the advantages of the Exoskeleton?
● Exoskeletons contain rigid and resistant components that offer protection against predators, bacterial attack and desiccation while on land.
●Exoskeletons contain rigid components that offer support enabling maintaining body shape.
●Exoskeleton of arthropods contains rigid framework of ingrowths known as apodemes which serve as attachment sites for muscles.
● In arthropods the exoskeleton is modified into appendages which offer more rapid locomotion than the hydroskeleton
● The arthropod exoskeleton contains various folds, flaps and parts modified for feeding and structures for respiration.
● Exoskeletons are often highly coloured for camouflage from predators, recognition by mates, and warning to scare off predators.
●The arthropod exoskeleton is jointed enabling flexibility in locomotion.
Give disadvantages of the exoskeletons
● Since exoskeletons are rigid and do not grow with the body, in arthropods they disrupt smooth and steady growth and so must be periodically shed to allow growth, which makes the animal temporarily vulnerable for predation and water loss by evaporation until hardening.
NB: Snails and many other mollusks solve that problem by continually enlarging their shells as they grow.
● An exoskeleton cannot support large sized animals because of their large volume and body mass in proportion to the cube of their linear dimensions, necessitating an impossibly heavy and thick exoskeleton.
●It requires modifications in movement. Many individual muscles are attached to the outer shell in order to create movement. In the appendages, these muscles are set up within multiple hinge joints, as these allow a wide range of motions.
Give the advantage of the endoskeleton
●Vertebrates have a versatile support system and as a result, they develop faster and bigger bodies than invertebrates.
● It’s jointed for flexibility to allow diverse range of locomotory patterns: swimming, digging, running, climbing, and flying, feeding (jaws).
●Endoskeleton does not limit space available for internal organs and can support greater weight.
●Bone are hard for protecting delicate parts like the brain, lungs, heart, spinal cord, etc.
●Bone tissue is mineralized and hence acts as mineral reserve for the body’s’ physiological processes.
●Mammalian bones manufacture the defensive leucocytes
Give disadvantages of endoskeleton
●Endoskeletons are enclosed in other tissues do not offer much protection from predators in some animals.
● Endoskeletons do not contribute to minimizing water loss from the body by evaporation
Describe locomotion in earthworms
●Crawling is initiated when circular muscles at the anterior end contract while longitudinal muscles relax segment by segment backwards as a wave along the body, there by exerting pressure on the coelomic fluid, which is forced to move at right angles to the squeezing circular muscles, while at the same time the chaetae retract inwards in this region of contracted circular muscles. The net result is forward extension of the anterior end.
●The movement of the fluid stretches the set of longitudinal muscles, which then contract to stretch the circular muscles back to the relaxed position, causing segments to elongate and thin.
●Forward extension of the anterior end is coupled with contraction of longitudinal muscles and relaxation of circular muscles in the more posterior segments causing body swelling and protrusion of chaetae this region.
●As the successive peristaltic waves approach towards the rear end of the body, longitudinal muscles in the anterior region contract, circular muscles relax, the chaetae protrude to anchor at the ground and pull the rear end forward.
●Control of muscle contraction is brought about by a complex network of inter and intrasegmental neurones
