Transcript Excretion and transport in other organisms

Excretion and transport in other
organisms
Unit 1 Area of Study 2 –
transport systems
Excretion in Freshwater Fish
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Unlike in humans, fish have a ready supply
of water to dilute nitrogenous wastes
In freshwater fish, water moves readily into
the gills (why?). This water is then used to
flush wastes out of the fish, in a dilute urine
Excretion in Saltwater Fish
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Because saltwater fish drink seawater, and this has
a large quantity of salt in it, salt is absorbed into the
fish’s body. This salt is then pushed back to the gills,
and back into the surrounding water. Any ammonia
wastes leave with this salt via the gills
Saltwater fish produce a very small amount of
concentrated urine, which contains salts and some
urea
Excretion in insects
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Insects have tubes called Malpighian
Tubules, which float in the blood. They
collect nitrogenous wastes, which are formed
into uric acid crystals (like hardened urea),
which enters the intestine and is excreted via
the anus.
Comparing excretory systems in
animals
Characteristic
Human
Fresh water fish
Salt water fish
Insect
Structure that filters
waste from blood
Nephrons in
kidneys
Nephrons in
kidneys
Nephrons in
kidneys and gills
Malpighian tubes
Length of loop of
Henle
Long
Virtually none
Long
Not applicable (no
kidneys!)
Type of urine (in
relation to normal
body fluids)
Hypertonic (high
salt concentration)
Hypotonic (low salt
concentration)
Isotonic (the same
salt concentration)
Extremely
hypertonic (crystals
– no water content)
Main nitrogenous
waste excreted
Urea
Ammonia (some
urea too)
Ammonia
Uric acid crystals
Comparing animal transport systems
(circulatory)
Feature
Mammal
Fish
Insect
Nature of system
Blood enclosed in vessels
that don’t directly contact
tissue cells
Blood enclosed in vessels
that don’t directly contact
tissue cells
Open system in which
blood directly bathes
tissue cells
Oxygen carrier
Pigment in Red Blood
Cells (haemoglobin) –
high oxygen carrying
capacity
Pigment in Red Blood
Cells (haemoglobin) –
high oxygen carrying
capacity
No function in carrying
oxygen in this system
Carbon dioxide carrier
In plasma is bicarbonate
ions. Some can bind to
haemoglobin
In solution in plasma
No function in carrying
carbon dioxide
Nutrient carrier
In solution in plasma
In solution in plasma
In solution in colourless
blood
Pumping mechanism
Four-chambered heart
Two-chambered heart
Single tube heart
Number of times blood
travels through heart
Twice per circulation
within the body
Once per circulation
within the body
Once per circulation
within the body
Transport in Plants
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We have already briefly looked at phloem
and xylem, and what they do.
Xylem – transports water from the roots to
other parts of the plant
Phloem – transports glucose and other
minerals around the plant, from the site of
photosynthesis
How do Xylem work?
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Xylem can use capillary action (the fact that
water molecules stick together and stick to
the tube’s walls) to move small amounts of
water
However, the quantity of water that needs to
be moved, and the direction it is moved in,
means that some energy is consumed in the
movement of water around the plant
This energy is provided by sunlight
Xylem continued…
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Gases enter and leave the leaves via
stomata. Water vapour also leaves via the
stomata, in a process called transpiration.
The cells within the leaf lose their water
when the stomata open. In turn, they are
replenished by the xylem opening, and this
water can then be lost through the stomata
An animation might help?
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http://www.sciencemag.org/sciext/vis2005/sh
ow/transpiration.swf
What about phloem?
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Soluble organic substances are transported
by phloem. This includes glucose.
Organic substances may be moved for use in
another area of the plant, or for storage for
later use
The movement of these substances around
the plant is called translocation.
Translocation requires energy
Use of sugars
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Many plants store sugars in the form of
starch (eg. Potatoes, bananas), for break
down and use for energy at another time.
Sugar can be used to build the subunits of
cells
Or it can be used as the energy source in
cellular respiration
Gas exchange in plants
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Stomata in the leaves open, allowing for
movement of gases in and out of the leaf, by
diffusion.
Remember: the opening of the stomata
depends on the hardness (turgor) of the
guard cells. The higher the water content, the
harder the cells. Water enters the guard cells
via osmosis.
Other plant gas exchange sites
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Lenticels – Small gateways in the stem for
gas exchange. Cells are loosely packed in
these areas and so gases like oxygen and
carbon dioxide can get through.
Root hair surface gas exchange – as well as
diffusion of water, some gases diffuse into
and out of the plant through the root hair
surfaces.
Excretion in plants
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Plants do not have advanced excretory
systems, as they can tolerate some
fluctuations in their environment. They tend
to instead store wastes in insoluble forms, in
vacuoles. These can be shed without
detriment to the plant.
Mammals vs Plants
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Large intake of food means a large amount
of waste produced. Mammals need to ingest
their nutrients, while plants largely make their
own food, and so mammals need more
advanced excretory systems for large
amounts of waste.