23.2 Animal Diversity
Bell Ringer:
In at least 3-5 sentences interpret this
quote:
"Ability is what you're capable of doing.
Motivation determines what you do.
Attitude determines how well you do it."
-Lou Holtz
American football coach
23.2 Animal Diversity
Bell Ringer
• 1-What are the four characteristics that all animals
share?
• 2-Animals are heterotrophs. How might this have
contributed to such great animal diversity?
23.2 Animal Diversity
KEY CONCEPT
More than 95 percent of all animal species are
invertebrates.
23.2 Animal Diversity
Each animal phylum has a unique body plan.
• Vertebrates have an internal segmented backbone and are in
phylum Chordata.
• Vertebrates make up less than 5% of all known animal species.
23.2 Animal Diversity
• Invertebrates do not have a backbone.
• Invertebrates encompass most animal groups. Each
group is defined by structural and functional
characteristics.
23.2 Animal Diversity
• Differences in body plans result from differences in the
expression of Hox genes.
– Hox genes tell embryonic cells which body part to
become (where limbs go or location of gut).
– Mutations in Hox genes led to the vast diversity of
animal species. These mutations can change the entire
body plan.
head
tail
fruit fly genes
human
HOX-B genes
head
tail
23.2 Animal Diversity
How are Hox genes related to
the diversity of body plans?
23.2 Animal Diversity
Animals are grouped using a variety of criteria.
• Three criteria are used to
categorize animals.
– body plan symmetry
– tissue layers
– developmental patterns
gastrovascular
cavity
mouth
mesoglea
brain
muscle
hearts
blood vessels
oral arms
mouth
segment
digestive track
nerve cord
tentacles
23.2 Animal Diversity
• There are two types of body plan symmetry.
– bilateral symmetry: body divides equally along one plane
Animals with
bilateral
symmetry can
be divided
equally along
only one
plane, which
splits an
animal
into mirrorimage sides.
23.2 Animal Diversity
• There are two types of body plan symmetry.
– radial symmetry: body arranged in circle around a
central axis
Animals with
radial symmetry
have body parts
arranged in a
circle around a
central axis.
23.2 Animal Diversity
• Bilateral animals have three
distinct layers of tissue (this
makes them triploblastic)
• radial animals have only two.
– both animal types have
ectoderm and endoderm
– bilateral animals have
mesoderm
• Animals are divided into two
major groups, protostomes and
deuterostomes.
– Protostomes form mouthfirst, and anus second.
– Deuterostomes first form the
anus and then the mouth.
Protostome
Deuterostome
23.2 Animal Diversity
A comparison of structure and genetics reveals the
evolutionary history of animals.
• Protostomes and deuterostomes are the two major
radiations on the animal phylogenetic tree.
NO
NOTISSUES
TISSUES
RADIAL
RADIAL
lancelets,
vertebrates
sea stars,
sea urchins
crustaceans,
insects, spiders
Echinodermata
Nematoda Arthropoda
Chordata
roundworms
clams, snails,
octopuses
Segmented
worms
flatworms
jellyfish, coral, anemones
Cnidaria Platyhelminthes Annelida
Mollusca
sponges
Porifera
DUETEROSTOMES
PROTOSTOMES
23.2 Animal Diversity
Porifera
Cnidaria
Platyhelminthes
Annelida
Mollusca
Echinodermata
Nematoda Arthropoda
Chordata
RADIAL
RADIAL
DUETEROSTOMES
PROTOSTOMES
NO
NOTISSUES
TISSUES
23.2 Animal Diversity
• The current organization of the animal kingdom shows
some unexpected relationships.
• Technological advancements
help to clarify evolutionary
relationships.
Systematics is a field
dedicated to the study of
relationships between
organisms because things
are constantly changing
due to new discoveries.
23.2 Animal Diversity
What evidence was used to
reorganize the animal kingdom?