Download BL 1021 – Unit 3-1

BL 1021 – Unit 3.1
Introduction to Animal Life
3.1.1 The Animal Cell
• Animals are a eukaryotic life form like plants and
fungi. However, unlike those other groups, animal
cells lack cell walls. This makes animal cells less rigid
and will often retain a spherical shape.
• Animals share many of the organelles that plants
have. However, animals lack the chloroplasts, and
thus cannot perform photosynthesis.
• As well, animals lack the large central vacuole. This
makes their cells less rigid but makes animals more
vulnerable to changes in the surrounding tonicity,
unless they have a protective coating.
3.1.1 The Animal Cell
3.1.2 Characteristics of Animals
• Animals as multicellular organisms composed of
tissues, organs and organ systems.
• The following characteristics describe at least most
animals:
•
• 1. All animals are multicellular.
• 2. The cells of an animal exhibit a division of labour.
In all but the simplest animals, cells are organized to
form tissues, and tissues are organized to form
organs.
3.1.2 Characteristics of Animals
• 3. Animals are exclusively heterotrophic; they ingest
their food first and then digest it inside the body,
usually within a digestive system
• 4. Most animals are capable of locomotion at some
time during their life cycle. (However, there are
some animals, such as sponges, that are sessile as
adults)
3.1.2 Characteristics of Animals
• 5. Most animals have well-developed sensory and
nervous systems and respond to external stimuli with
adaptive behaviour.
•
• 6. Most animals reproduce sexually, with large, nonmotile eggs and small flagellated sperm. Sperm and
egg unite to form a fertilized egg, or zygote, which
goes through a series of embryonic stages before
developing into a larva or immature form
3.1.3 Body Plans
• Complexity: the level that an animal has multiple
tissues of different purposes. More complex
organisms will have more organs and organs more
specialized for specific tasks.
• Body Symmetry: If an organism can be split by an
imaginary line with an equal amount on each side.
• Bilateral symmetry: there is only one line that can
divide the organism into equal halves
• Radial symmetry: there are many lines that can cut
the organism into equal parts, all the lines are about
an axis.
3.1.3 Body Plans
3.1.3 Body Plans
• All animals begin as a
zygote that divides
over and over. During
the embryonic stage,
animals can have up to
three major germ
layers. These layers
specialize into the
innermost, middle, and
exterior layers of an
adult organism.
3.1.3 Body Plans
• Body Cavity (coelom): a fluid-filled space between
the digestive tract and the outer body wall.
• In the simplest of animals, this is not even present. In
more developed animals, it partially developed
and in the most complex creatures this is a large
space for organs to develop and move.
• The body cavity is an internal space where organs
can grow, develop and move independently of the
outer wall.
3.1.3 Animal Phyla
• The next level of organization below kingdom is
phyla. Each phyla contains a wide variety of
creatures grouped by similar complexity and body
symmetry.
• The nine major phyla of animals are arranged by
increasing complexity. As complexity increases,
interdependence of cells increases, and organs
become more specialized. For example,
fragmentation is only possible with the first few
phyla.
3.1.3 Animal Phyla
• Porifera
• Example: Sea sponges
• Lack tissues, cells are
loosely held together.
• Often made of just cell
layers and a jelly
• No coelom, but water
does flow through
random openings
• Most lack symmetry, but
some are radially
symmetrical.
3.1.3 Animal Phyla
• Poriferans are generally
non-moving and
depend on currents to
move water through
them to obtain food
and oxygen.
• Poriferans represent the
most basic animal – a
two-layered tube with
only one opening.
3.1.3 Animal Phyla
• While poriferans are the
most basic of animals,
they still have some
division of labour/cell
specialization.
• Due to the relative
simplicity of the animal,
these cells are able to
change roles.
3.1.3 Animal Phyla
• Cnidaria
• Examples: Jellyfish, sea
anemones, hydra
• Radially symmetrical
• Two distinct tissue layers
are present – an inner
surface (digestive) and
outer surface (epidermis).
• No coelom.
3.1.3 Animal Phyla
• The general form of a
cnidarian is of a tube
with a single opening.
Food both enters and
leaves through this
one orifice.
• Some neural tissues
and muscle sets are
present – making
them significantly
more specialized than
poriferans.
3.1.3 Animal Phyla
• Many cnidarians can
reproduce by budding –
by growing an entire
second clone on the
main body and then
detaching it.
• Cnidarians also
reproduce sexually and
can have complex life
cycles (both a polyp
and medusa
form, hermaphroditism,
etc)
3.1.3 Animal Phyla
• Platyhelminthes
• Examples: Planarians,
flatworms
• Bilateral symmetry –
have a definite head
and tail.
• Even though they have
an elongated shape,
they only have one
digestive opening like
cnidarians.
3.1.3 Animal Phyla
• As these animals lack
complex respiratory
and circulatory
systems, they take on a
very flat shape to allow
oxygen and nutrients to
move by diffusion.
• Diffusion is not
powerful/fast enough
to support thicker
forms.
3.1.3 Animal Phyla
• Bilateral animals show
cephalization – a trend
of focusing sensory
organs and nervous
tissue towards the
head.
• In simpler creatures like
platyhelminthes, there
is more nervous tissue
at the brain region, but
not nearly to the
proportion of humans.
3.1.3 Animal Phyla
• The platyhelminthes are
simple enough to
survive fragmentation.
Even though they have
a head, the body is so
generally uniform that
the sections could
continue on living long
enough to regrow the
missing tail/head.
3.1.3 Animal Phyla
• Nematoda
• Example: Roundworms
(non-segmented worms)
• Bilateral symmetry
• This is the first group we
have looked at with a
linear digestive tract with
two openings (separate
mouth and anus). Food
travels in one direction
only.
3.1.3 Animal Phyla
• Nematodes have all
three full embryonic
tissue layers.
• A proper coelom is
lined with tissue on all
sides. Nematodes have
a body cavity, but the
inner germ layer is
“exposed”. It is
considered a pseudocoelom. (pseudo =
fake)
3.1.3 Animal Phyla
• Nematodes are further cephalized and are generally
more specialized along the body than
platyhelminthes.
• Thus, they are much less likely to survive
fragmentation.
3.1.3 Animal Phyla
• Mollusca
• Clams, snails, slugs
• Soft body with mineral
shell.
• Have a true coelom
• Have true tissue systems
• Bilateral symmetry
3.1.3 Animal Phyla
• The standard mollusk is
a very soft organism
with a hard protective
shell.
• While mollusks are very
cephalized, many have
their breathing/waterfiltering structures to
their rear rather than at
the head region.
3.1.3 Animal Phyla
• Many mollusks have a
singular foot with
various muscles that
allow it to move.
• Marine mollusks may
have this foot adapted
into tentacles or a shell
opening/closing
muscle.
3.1.3 Animal Phyla
• Annelida
• Segmented worms,
leeches
• Coelomates.
• Bilaterally symmetrical.
• Full tissue systems.
3.1.3 Animal Phyla
• Arthropoda
• Insects, spiders,
crustaceans
• Bilaterally symmetrical
• Coelomates
• Full tissue layers.
3.1.3 Animal Phyla
• Arthropods are known
for their hard
exoskeletons. (exo =
outside).
• These exoskeletons
allow for strong and
complex body
structures – claws, legs,
tails, shells, heads, etc.
3.1.3 Animal Phyla
• Many arthropods have
to periodically shed
their exoskeleton to
give themselves room
to grow. A new, larger
exoskeleton will then
solidify on the organism
later once it has grown.
3.1.3 Animal Phyla
• Echinodermata
• Are bilaterally
symmetrical during
embryonic
development but often
take on radial
symmetry in adulthood.
• Coelomates.
• Three full tissue layers.
3.1.3 Animal Phyla
• Echinoderms have a
variety of internal
calcium-based
skeletons.
• Some echinoderms use
the coelom as a
circulatory system,
pumping fluids around
in this space rather
than in dedicated
vessels.
3.1.3 Animal Phyla
• This water-based
vascular system can
also be used for
movement (using a
system similar to
hydraulics) as well as
gas exchange
(respiration).
3.1.3 Animal Phyla
• Chordata
• Examples: fish, lizards,
birds, mammals
• Many have a
backbone, but not all.
• Most diverse phylum.
• Bilateral, coelomates, 3
tissue layers.
3.1.3 Animal Phyla
• All chordates have the
following features:
• A hollow nerve cord
running along the
back.
• This transfers
information to and from
a brain.
• A spine of bone or
cartilage protects the
nerve cord.
3.1.3 Animal Phyla
• All chordates have a
notochord – a flexible rod
between the digestive
tract and nerve cord.
• This served as the first
prototype of the true
backbone.
• In most modern
chordates, the notochord
will develop into a part of
the spine, although some
animals retain a
notochord into
adulthood.
3.1.3 Animal Phyla
• All chordates will also
have pharyngeal slits.
• While they resemble gills
in the embryo, they
develop into the ears,
jaws and throat
(pharynx).
• All chordates also have a
post-anal tail in
embryonic form. This can
develop into many forms
as an adult, or may be
reduced/lost.
3.1.3 Animal Phyla
• The field of
comparative
embryology studies the
similarities of all animal
embryos.
• The fact that there are
so many similarities in
both form and function
is strong evidence for
common ancestry.
3.1.4 Vertebrates
• Vertebrates are a subphyla of chordates that have
a strong bone or cartilage spine protecting their
nerve cord.
• All other animals are called invertebrates.
• The backbone is vital in allowing animals to be
stronger, more powerful and quicker. The
backbone acts as a base frame for muscles to
attach to.
3.1.7 Adaptations of Vertebrates
• Fish
• Have jaws – a hinged bone structure that allows for
high-pressure biting and chewing.
• Use 2 pairs of fins to steer and swim
• Use gills to absorb oxygen and release carbon
dioxide with the water.
• Fish come in two types – depending on the
materials making up the skeleton.
3.1.7 Adaptations of Vertebrates
• Cartilaginous Fish
Sharks, rays
Cartilage-based skeleton
Have a very powerful sense of smell.
Use electrosensors in their head to “feel” nearby
animals by detecting the small magnetic fields
created by muscle contractions of other animals.
• A lateral line system of sensors along the sides of
the body allow fish to sense vibrations in the water.
•
•
•
•
3.1.7 Adaptations of Vertebrates
Bony Fish
Fish with skeletons
Also have excellent sight and sense of smell
Have an operculum, a flap that can cover the gills
for protection. This flap also can direct water
through the gills while the fish is not moving –
allowing it to “breathe” without moving, something
which other fish cannot do.
• Use a swim bladder to store gas to maintain
buoyancy. This allows them to float at a certain
depth without constantly swimming.
•
•
•
•
3.1.7 Adaptations of Vertebrates
• Amphibians
• Frogs, salamanders, toads
• Begin life as fish-like with gills
• Undergo metamorphosis into land animals with
lungs
• Have very thin skin that needs to stay wet and can
do some gas exchange
• Have eardrums for hearing
3.1.7 Adaptations of Vertebrates
• Reptiles
• Lizards, snakes
• Have scales made of keratin that prevent water loss
and protect
• Only use lungs to breathe
• Use water-filled, hard-shelled eggs that can survive
on land.
• Are cold-blooded (ectotherms) and absorb body
heat from sunlight rather than generating it
internally.
3.1.7 Adaptations of Vertebrates
• Birds
• Also lay hard-shelled eggs
• Have scales on feet and legs
• Highly specialized for flight:
o Bones have a honeycomb structure for strength
and low weight
o Lack teeth (less weight)
o Airfoil-shaped wings to make them aerodynamic
o Powerful breast muscles to power the
movements of flight.
3.1.8 Mammals
• Features common to all mammals:
• Land-based, breathe with lungs
• Warm-blooded (endotherms), set their own body
temperature, create their own heat
• Hair – used to insulate the body to maintain a
constant temperature. Can also be used to cool
the body
• Mammary glands – milk-producing glands that are
used to nurse offspring
3.1.8 Mammals
• There are 3 types of mammals:
•
•
•
•
Monotremes
Example - platypus
Egg-laying mammals
Will lie on their eggs to provide warmth, then nurse
the young with milk secreted from the mother’s fur.
3.1.8 Mammals
• Marsupials
• Have a short gestation period and then give birth to
very small, embryonic offspring.
• These attach to the mother’s nipples and develop
inside the marsupium – the pouch.
• Example - kangaroo
3.1.8 Mammals
• Eutherians/Placentals
• Offspring develop within the mother for an
extended period of time until fully developed.
• During this time they feed off the mother using a
placenta
• Offspring are born more capable of survival than
other types of mammals.
• Most successful mammals as the offspring are best
able to survive once born.
• Example - humans