Introduction to Animals
• Over a million different types have been
identified!
• Animals likely evolved from protozoans.
Kingdom Protista
Characteristics of Animals
All animals share these general features:
1. heterotrophy,
2. mobility,
3. multicellularity,
4. sexual reproduction,
5. diploidy,
6. the absence of a cell wall,
7. cells organized as tissues, and
8. blastula formation.
heterotrophy,
Can’t make their own food… must eat
things.
mobility,
• Animals can swim, crawl, walk, run, and
even fly.
• Some only move in the larval stage… the
sponge
multicellularity,
• Made up of more then one cell!
• Although animals come in a wide range of
sizes, the cell sizes are all very similar!
sexual reproduction
• Almost all animals reproduce sexually by
producing gametes.
• Unlike the egg cells, the sperm cells of
animals have a flagella and are highly
mobile.
diploidy,
adults have two copies of each
chromosome, one inherited from their
father and one from their mother.
the absence of a cell wall,
Among the cells of multicellular organisms,
only animal cells lack rigid cell walls. The
absence of a cell wall has allowed animals
mobility that other multicellular organisms
do not have.
blastula formation
In all animals except sponges, the zygote
(fertilized egg cell) undergoes cell divisions
that form a hollow ball of cells called a
blastula.
cells organized as tissues
Cells within the blastula eventually develop into
three distinct layers of cells endoderm, ectoderm,
and mesoderm . These layers are called the primary
tissue layers because they give rise to all of the
tissues and organs of the adult body.
tissues
tissues are groups of cells with a common
structure that work together to perform a
specific function.
Body Symmetry
All animals have their own particular body
plan, a term used to describe an animal’s
shape, symmetry, and internal
organization.
3 body symmetry
Asymmetry.
Animals that grow in an irregular pattern,
such as a sponge, show asymmetry.
radial symmetry
Animals with radial symmetry have body
parts arranged
around a central axis.
bilateral symmetry
Animals with bilateral symmetry have
a distinct right and left half, and most display
cephalization.
body plans
Animals have one of three basic body plans:
acoelomate, pseudocoelomate, and
coelomate.
coelom
a body cavity, coelom
or (SEE luhm), a
fluid-filled space
found between the
body wall and the
digestive tract (gut).
This space is lined
with cells that come
from mesoderm.
• Coelomates are either protostomes or deuterostomes.
• Protostomes (first mouth) are coelomates whose
embryonic development shows a blastopore associated
with a mouth.
• Deuterostomes (second mouth) are coelomates whose
embryonic development shows a blastopore associated
with an anus, with a second opening forming the mouth
(hence "second mouth").
acoelomate
Animals with no body cavity
are called acoelomate (ay
SEEL oh mayts).
The space between an
acoelomate’s body wall and
gut is completely filled with
tissues
pseudocoelomate
have a body cavity located
between the mesoderm
and endoderm. Their
body cavity is called a
pseudocoelom (false
coelom)
Body plans
Segmentation
Segmentation in body structure underlies
the organization of all advanced animals.
• Some animals have their bodies divided
into segments. This allows them to
specialize certain segments, such as for
antennae, eyes, claws, etc. Humans,
insects, and earthworms are examples of
segmented animals.
animal phyla
There are about
35 animal
phyla, which
contain an
extraordinary
range of body
forms and body
systems.
.
phylogenetic tree
To visually represent the relationships
among various groups of animals,
scientists often use a type of branching
diagram called a phylogenetic tree.
It shows how animals are related through
evolution
Scientists classify animals using several
different types of data, which include
comparing anatomy and physiology,
patterns of development, and DNA.
• The animal kingdom is divided in two
groups: vertebrates and invertebrates
Animal Body Systems
Body systems are specialized to carry out
different tasks.
Levels of organization:
Cells
tissues
organs
organ systems
organisms
Digestive systems
• Simple animals have a gastrovascular
cavity with only one opening, while morecomplex animals have a one-way gut.
Respiration/ gas exchange
Simple animals exchange gases directly
through their skin.
More-complex aquatic animals use gills,
while terrestrial animals use a variety of
respiratory organs, such as lungs.
circulatory system
In an open circulatory system, circulatory
fluid leaves the vessels and enters the
body cavity.
In a closed circulatory system, blood
remains in the vessels.
open circulatory system -- primitive system found in insects and crustaceans -blood not always contained in blood vessels -- heart pumps hemolymph (blood
and cell fluids) into vessels, but vessels empty into large cavities or sinuses
containing organs -- blood diffuses through tissues and back into heart.
closed circulatory system -- found in higher animals -- system is
"closed" because the blood is always contained in vessels.
Nervous System
While simple animals have little coordination
among their nerve cells, complex animals
have nerve cords and a brain with
associated sensory structures.
Excretory System
For most animals, eliminating wastes is
linked to maintaining the correct water
balance in their body.
Skeleton/Support
Hydrostatic support
Exoskeleton
Endoskeleton
Frog
Asexual
Asexual reproductive methods include
fragmentation, splitting in two, and
parthenogenesis.
Reproduction that does not involve the fusion
of two gametes is called asexual
reproduction. A sponge, for example, can
reproduce by fragmenting its body. Each
fragment grows into a new sponge.
Some species of sea anemone reproduce by
pulling themselves in half, forming two new
adult anemones
sexual reproduction
In sexual reproduction, male and female
gametes combine to form a new individual
Human Reproduction
• Eggs produced in the ovary are fertilized in the
fallopian tube and implant in the uterus. Sperm,
made in the testes by spermatogenesis, a form
of meiosis, must fertilize the haploid egg for it to
develop into an embryo.