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The Circulation of
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LEARNING COMPETENCIES
1. Compare and contrast the circulation
of plants and animals.
2. Identify the different organ systems
present in plants and animals
3. Explain how an organ system works
with another organ systems
4. Differentiate the animal and plant
organ systems
5. Describe the function of each system
found in plant and animals
In biology transport means carrying
substance absorbed or made in the body
of an organism to all other parts of its
body. The circulatory system is the
primary method used to transport
nutrients and gases through the body.
The circulatory system is effectively a network
of cylindrical vessels: the arteries, veins, and
capillaries that emanate from a pump, the heart.
In all vertebrate organisms, as well as some
invertebrates, this is a closed-loop system, in
which the blood is not free in a cavity. In a
closed circulatory system, blood is contained
inside
blood
vessels
and
circulates
unidirectionally from the heart around the
systemic circulatory route, then returns to the
heart again.
As opposed to a closed system, arthropods– including
insects, crustaceans, and most mollusks– have an ‘open’
circulatory system. In an open circulatory system, the blood
is not enclosed in blood vessels but is pumped into an open
cavity called a hemocoel and is called hemolymph because
the blood mixes with the interstitial fluid. As the heart beats
and the animal moves, the hemolymph circulates around
the organs within the body cavity and then reenters the
hearts through openings called ostia. This movement allows
for nutrient exchange, and in some organisms lacking direct
gas exchange sites, a basic mechanism to transport gasses
beyond the exchange site.
Circulatory System Variation in Animals
The circulatory system varies from simple systems in
invertebrates to more complex systems in vertebrates. The
simplest animals, such as the sponges and rotifers , do not need
a circulatory system because diffusion allows adequate
exchange of water, nutrients, and waste, as well as dissolved
gases. Organisms that are more complex but still only have two
layers of cells in their body plan, such as jellies and comb jellies
also use diffusion through their epidermis and internally
through the gastrovascular compartment. Both their internal
and external tissues are bathed in an aqueous environment and
exchange fluids by diffusion on both sides. Exchange of fluids is
assisted by the pulsing of the jellyfish body.
For more complex organisms, diffusion is not efficient for
cycling gases, nutrients, and waste effectively through the
body; therefore, more complex circulatory systems evolved. In
an open system, an elongated beating heart pushes the
hemolymph through the body and muscle contractions help to
move fluids. The larger more complex crustaceans, including
lobsters, have developed arterial-like vessels to push blood
through their bodies, and the most active mollusks, such as
squids, have evolved a closed circulatory system and are able
to move rapidly to catch prey. Closed circulatory systems are a
characteristic of vertebrates; however, there are significant
differences in the structure of the heart and the circulation of
blood between the different vertebrate groups due to
adaptation during evolution and associated differences in
anatomy.
In amphibians, reptiles, birds,
and mammals, blood flow is
directed in two circuits: one
through the lungs and back
to the heart, which is called
pulmonary circulation, and
the other throughout the rest
of the body and its organs
including the brain (systemic
circulation). In amphibians,
gas exchange also occurs
through the skin during
pulmonary circulation and is
referred to as
pulmocutaneous circulation.
Transport in plants – plants are the
type of organisms that have an
autotrophic mode of nutrition. By
taking in carbon dioxide from the
air, minerals, and water from the
soil, plants make their own food.
After that, they release oxygen and
water vapor. This process is
Photosynthesis.
By this process, plants synthesize their food
in the leaves. For trees, leaves are
considered to be food factories. For the
process of photosynthesis, raw materials
should be transported to the leaves. For
transport in plants, they need a transport
system to move food, water, and minerals
around because for them no heart, no blood,
and since these plants do not have a
circulatory system, transportation makes up
for it.
In plants, there are pipe-like vessels through which
water and minerals can enter the plants. These
vessels are made up of elongated cells and thick
walls. A group of cells forms a tissue that performs a
specialized function within the organisms. These are
conducting tissues. These conducting tissues are
divided into two types which are xylem and phloem.
Xylem: It is a vascular
tissue that spreads from
the top to bottom of the
plant. For the transport of
water molecules, it helps a
lot. It also plays a vital role
in the case of dissolved
substances from the root
hairs to aerial parts of the
plant. It transfers water in
one direction. Commonly,
xylem occupies the central
part of the vascular
bundle. It mainly includes
different types of cells
such as tracheid, vessels,
and xylem parenchyma
and xylem fibers.
Phloem: It is also vascular
tissue. In a plant where the
necessity of food
molecules is there, the use
of the phloem
transportation process will
take place. Some elements
are there in the phloem
such as sieve elements,
phloem parenchyma,
fibers, and companion
cells. The transportation
process in this tissue is
bidirectional. In association
with xylem, it forms
vascular bundles. The
edges of vascular bundles
are occupied by phloem.