Download Living In Water

Introduction
 What is a species?
 A species is a group of individuals sharing some common
characteristics or qualities, and whose offspring also share those
characteristics or qualities
 All species are specifically suited for the lives they lead.
 Examples:
 Humans have legs, allowing effective movement on land
 Mallards are fliers with wings, which allow them to move through the air
 Bluegills are swimmers with fins enabling them to swim in water
 The things that enhance a species’ chance of survival in a specific
environment whether it is behavioral, structural, or a
physiological trait, is called an adaptation.
 All living things have adapted to the environment in which they
live.
 Aquatic organisms live in water and have adaptations to live in
specific aquatic environments and conditions
Fish Guts
 What is it that is special in fish to allow them to survive in
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water?
Fish are endothermic.
Endothermic means their body temperature changes as the
surrounding water temperature changes
The body temperature of most fish remains very close to
the temperature of their water habitat.
Since temperature has such a great effect on fish, different
species have different water temperature preferences.
Some fish species prefer warmer water than others. In
Texas, most fish species are warm water fish because most
of Texas’s waterways are warm. This is similar to all fish as
you move nearer the equator.
Fish Guts (cont’d)
 Fish have many of the same internal organs as
humans and other animals.
 They have a heart to pump blood
 intestines and stomach to digest food
 kidneys, a liver, a gall bladder, and a spleen
Fish Guts (cont’d)
 A unique physiological adaptation fish have that enable them to
live in freshwater or saltwater is osmoregulation.
 This is how fish regulate their intake of saltwater or freshwater to
keep their fluids, such as blood, from becoming too salty or too
dilute
 Fish living in saltwater have internal fluids lower in salts than the water in
which they live. These fish must drink large amounts of saltwater and
excrete small amounts of fluids while they actively secrete high amounts of
salts through their gills.
 Fish in freshwater have higher body fluid salt concentrations than the
surrounding water causing them to excrete large volumes of low salt
content fluids and take up salts through their gills.
 Some aquatic species are able to adapt to a wide range of salinities. Fish that
can live in freshwater, brackish, and saltwater are called euryhaline.
 Examples of common euryhaline aquatic species in Texas are red drum
and blue crab.
Fish Guts (cont’d)
 Although fish have many of the same organs as humans
and animals, they obviously have some organs that allow
them to live in water.
 Instead of lungs, fish have gills. Gills contain capillaries
(fine blood vessels) that take up dissolved oxygen and
release carbon dioxide.
 This is done as water enters through the fish’s mouth,
passes over the gills, and exits from the fish. In clean,
moving water, a fish can absorb up to 85% of the dissolved
oxygen available in well-oxygenated water.
 Fish and amphibians are the only vertebrates (animals
with a backbone) that are able to live their entire lives
completely submerged in water.
How Fish Swim
 Up to 80% of a fish’s body is made of muscle. In
comparison, only 30-40% of human body weight is muscle.
A fish’s muscles are packed along its sides. That is where a
fish’s swimming power comes from.
 As an example, when a largemouth bass wants to move
forward, it begins a side-to-side wiggle that starts at its
head and moves backward along its body. The wiggle
pushes water behind the fish, which propels it forward.
How Fish Swim (cont’d)
 Fish also use their many fins to move about in the
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water.
Fish have two sets of paired fins, called the pectoral
and pelvic fins, along the side.
They also possess a single caudal and anal fin.
Some fish species have a single dorsal fin, while others
have two.
Certain fish (such as freshwater trout and catfish) also
have an adipose fin which is located on their back,
behind the dorsal fin.
Fish Fins
 The dorsal fin is located along the back of the fish. It helps keep
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the fish upright and stable.
Some species of fish, such as sunfish, have sharp spines of their
fins. This helps to discourage other fish from eating them.
Underneath the fish near the anus, is the anal fin which helps
with stabilization.
The caudal fin (a.k.a. tail fin) can be rounded, forked, or crescent
shaped. No matter the shape, the purpose is to help with speed
and movement.
Most fish use their pectoral or pelvis fins, which are located
along their sides, to steer or maneuver. These fins can move
independently, giving the fish the ability to move quickly in any
direction.
In general, fins can be used as brakes or rudders to help the fish
stop, turn, go up or down, or even go backward.
Fish Fins
 The fish’s body shape also affects how they are able to
maneuver through water. Certain body shapes may
help a fish survive by allowing it to move in and out of
tight places to catch food or to escape from predators.
 Fish with a flat body shape mostly live and feed on the
bottom.
 Torpedo-shaped fish are built for speed.
 Fish with a tall and thin shape can easily slip in and out
of tight places.
Sink or Swim
 Many freshwater and saltwater fish have swim bladders.
 Most of the time, the fish uses its swim bladder to keep
from sinking.
 Being able to float or rise in water is referred to as
buoyancy.
 The swim bladder works a like a hot air balloon. The more
gas (oxygen) it contains, the higher a fish will suspend or
float in the water.
 Some species of fish can also move their swim bladder to
make sounds to communicate during courtship, to defend
its territory, or as an alarm when it has been disturbed.
Swim Bladder
Fish Skin
 Many species of fish are covered
with scales that protect them like
roof shingles protect a house.
 There are four main types of
scales with many variations to
each of these.
 Fish don’t grow more scales as
they get older, the scales just get
bigger.
 Fish biologists can estimate the
age of some fish by counting rings
on a scale, similar to the way
foresters can tell a tree’s age by
counting its growth rings.
Fish Skin (cont’d)
 Fish skin is often coated with slime, which helps reduce friction
as fish swim through the water. The slime also helps protect
them from disease.
 Many fish species have counter-shading, often being darkcolored on top and light-colored underneath.
 This aids in camouflaging fish.
 For example, a darter is very difficult to see on a gravel streambed
because of its ability to blend into its multicolored surroundings.
Fish Sense
 Fish have senses similar to ours. The senses of some
fish are more developed than others.
 Some fish use their sense of smell or taste to find food.
 Others feed primarily by sight.
 The placement and shape of eyes of some fish species allow
them to see almost all the way around their bodies.
 Although fish are nearsighted (cannot see far away) it is
difficult to sneak up on a fish because they see in all
directions.
 Fish can see colors.
 Fish that feed at night or live on the bottom in very deep
or turbid water rely heavily on their senses of smell and taste,
instead of on sight.
Fish Sense
 Fish can also hear, plus they have a special row of sense
organs called the lateral line that give them the
ability to hear low-frequency sounds.
 A fish’s ears are located beneath the skin on either side of the
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head.
The lateral line is used to detect movement and vibration in
the water.
Special hair-like cells along the lateral line, either free
standing or located inside very small fluid canals, are very
sensitive to vibrations in the water.
The lateral line can be seen on many fish as a faint line
running along its side.
Lateral lines serve an important role in detecting prey or
predators, schooling and orienting to objects in the water.
Life in the Water
 Fish have been on Earth for more than 400 million years.
 Today there are more than 36,000 species identified
worldwide.
 They are divided into three major classes:
 (1) jawless fish which include lampreys;
 (2) cartilaginous fish which include sharks and rays, and
 (3) the largest group called bony fish.
 In Texas alone, there are over 250 species of freshwater fish
and 1,500 species of saltwater fish in the Gulf of Mexico.
 Different species of aquatic life are adapted to play different
roles in the aquatic environment. Just like fish, many
species of invertebrates, amphibians, reptiles, mammals,
and birds have adaptations that allow them to survive
in aquatic ecosystems.
Aquatic Invertebrates
 There are many kinds of aquatic invertebrates, ranging
from giant squid and clams, to squirmy
insect larva that live in the mud, to tiny free
swimming zooplankton.
 Invertebrates make up much of the food that larger
aquatic organisms eat.
 In addition to being part of the food web, aquatic
invertebrates help breakdown organic matter.
Aquatic Invertebrates
 They are excellent indicators of the health of an
aquatic habitat. Species can range
from pollution tolerant to extremely sensitive to
pollution.
 Some aquatic insects have small gills along the body or
tail, others have little holes along their body to absorb
dissolved oxygen from the water, some use breathing
tubes they raise from the water into the air, while
others can carry a small bubble of air underwater with
them from the surface.
Aquatic Invertebrates - Molluscs
 Molluscs are species that
live in freshwater and
saltwater and are
extremely varied in form.
 Some mollusks, including
clams, oysters, scallops,
mussels, and snails, have
hard shells.
 Others like the octopus
have soft bodies and tend
to live in cavities for
protection, while squid
which also have soft
bodies are free swimming
species.
Aquatic Invertebrates - Insects
 Aquatic insects are found only in freshwaters and the shallow
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brackish waters of estuaries and bays.
These invertebrates have at least two phases of life. Insects
change form through a process called metamorphosis.
For insects such as many mayflies, stoneflies, dragonflies,
and damselflies the larvae or nymph phase is usually spent
entirely in water, while the adult phase may be spent in water,
on land, or in the air.
Many adult aquatic insects have large wings that allow them
to fly about.
While there are no aquatic insects that can live entirely in
saltwater, there are many that inhabit brackish water
estuaries and bays. An example is saltwater mosquitoes.
Aquatic Invertebrates - Insects
 Mayfly nymph
and adult
 Video: Aquatic
Insects,
https://www.yo
utube.com/wat
ch?v=qSNXRxJWTc
(10:50)
Aquatic Invertebrates - Crustaceans
 Crustaceans also live
in both freshwater
and saltwater. They
have an exoskeleton,
which is an outer
covering that supports
and protects the
animal’s body.
 Familiar crustaceans
are crayfish in
freshwater, and
shrimp and lobster in
saltwater.
Aquatic Invertebrates - Plankton
 Plankton are tiny invertebrates
and photosynthetic organisms
that are carried about by flowing
waters or ocean currents.
 Animal plankton are called
zooplankton and are made up of
tiny crustaceans and even tinier
animals called rotifers.
 Some species can be as large as
your fingernail, but most are so
small you need a microscope to
see them.
 Zooplankton are important food
for small fish
Aquatic Invertebrates - Plankton
 Crustacean
Zooplankton, Daphnia
Aquatic Plants and Algae
 Aquatic and wetland plants come from several land plant
families and have acquired similar special adaptations to
allow for life in water.
 The most common adaptation is large air spaces or channels
running through the leaves, stems, and roots. These air
channels allow an exchange of gases between the parts of the
plant that remain submerged in water, such as the root, and
the parts that reach above the water’s surface.
 Other adaptations are floating leaves and leaves divided into
many deep, narrow segments.
 Aquatic plants fully adapted for a life in water can only grow
in water or in soil that is saturated with water.
Aquatic Plants and Algae
 A few aquatic plants are able to survive in brackish or
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saltwater, but only in shallow areas.
Several species of seagrass are found in Texas’ bays and
estuaries.
Seagrass beds are important to the estuarine food
chain.
Decomposing seagrass leaves provide nutrients for
small shrimp, crabs, and fish and seagrass leaves provide
protective cover for these small animals.
Waterfowl, such as redhead ducks also feed on seagrass
leaves and roots.
Aquatic Plants and Algae
 Seaweed in the ocean and estuaries is often confused
with aquatic plants, but seaweed is not a vascular plant.
It is really multicellular algae.
 There are many forms of algae some of which are so
small they can only be seen with a microscope. These
algae are part of the phytoplankton in freshwater and
saltwater.
Living in Water Video
 http://www.youtube.com/watch?v=Sp-Hjc5v-cY