Reading Check 26.1 Characteristics of animals
Complete this outline while you read section 26.1 of your textbook. You do
not need to answer in complete sentences.
General features of animals
The largest living animal is the ________________________, but some animals, like the
________________________, are microscopic in size.
List three characteristics of all animals:
________________________________________________________________________________________________
Most animals have many types of ________________________, and groups of them can take on special shapes
and functions in order to work together.
Because animal cells lack a cell wall, animals often have greater ________________________ than other organisms.
Most animals move around their ________________________ to look for food. Other animals, called
________________________ ________________________, do not move but catch particles of food that drift by in the
water.
________________________, the ability to move from place to place, is a big advantage for most
animals. It helps them to find ________________________ and favorable ________________________ and
helps them to avoid ________________________. Some animals, like ________________________ and
________________________, do not move, but attach themselves to surfaces.
Kinds of animals
Kingdom Animalia contains about _____ major phyla. In addition, they are often informally grouped
as ________________________ or ________________________. The vast majority of animals are
________________________. Vertebrates make up only one subgroup of the phylum
________________________.
________________________ includes any animal that does not have a backbone.
________________________ are ________________________ that have a backbone.
________________________ are the individual segments that make up the backbone. The backbone
supports and protects a dorsal ________________________ ________________________ and provides a site
for ________________________ attachment. This complex ________________________ allowed some vertebrates to
grow much larger than their invertebrate ancestors.
In the space below, briefly describe the significance of the image above. How does it relate to this section of
the textbook?
Reading Check 26.2 Animal body systems
Complete this outline while you read section 26.2 of your textbook. You
do not need to answer in complete sentences.
Support
An animal’s ________________________ provides a framework that supports its body. This structure is
also vital to an animal’s ________________________.
Define each type of skeleton AND list one organism that has it
Hydrostatic skeleton
________________________________________________________________________
Exoskeleton
________________________________________________________________________
Endoskeleton
________________________________________________________________________
Digestive and excretory systems
The digestive system is responsible for extracting ______________________ and ______________________ from an
animal’s food.
Sponges, which are animals that lack a digestive system, digest their food within their body
________________________. All other animas digest their food outside their cells within a digestive
________________________. Simple animals have a ________________________ cavity with only one
opening, where ________________________ goes in and ________________________ go out. More complex
animals have a one-way digestive ________________________, or gut, where food moves from the
________________________ to the ________________________.
________________________ is the removal of waste products like ________________________, which can be harmful if
they are not removed. Organisms that live in the water excrete
________________________ into the water. Animals that live on land, though, need to minimize
________________________ loss, and so they convert ammonia to less ________________________
chemicals before passing them out of the body. This way, ________________________ and other useful
substances can be returned to the body without being excreted.
Nervous system
The nervous system carries information about the ________________________ through the body and
coordinates ________________________ and ________________________. Nerve cells carry messages in
the form of ________________________ impulses.
A simple arrangement of nerve cells is called a ________________________ net, and the nerve cells do
not coordinate actions directly. More complex clusters of nerve cells, called ______________________, can
coordinate responses. Complex invertebrates and vertebrates have true
________________________ with sensory structures associated with them.
continued on next page 
Respiratory and circulatory systems
The respiratory system exchanges ________________________ and carbon dioxide between the body
and the environment. Many aquatic animals respire using ________________________, while terrestrial
animals can respire using a variety of respiratory organs, including ________________________.
The circulatory system transports ________________________ and ________________________, along with other
substances, within the body. Some small animals do not require a circulatory system
because their ________________________ can obtain these necessities directly. Larger animals have
________________________ located far from the sources, and so they must transport nutrients and wastes to and
from these cells.
In an open circulatory system, a heart pumps fluid containing oxygen and nutrients into the body
________________________. From there, the fluid washes across the body’s ________________________.
In a closed circulatory system, a heart pumps blood through a system of blood ___________________.
Reproduction
Asexual reproduction occurs when an individual produces ________________________ copies of itself
and does not mix its ________________________ with those of another. Sexual reproduction occurs
with the union of a male and a female ________________________. These special haploid cells are
produced in the sex ________________________. The ________________________ produce sperm, and the
________________________ produce eggs.
In the space below, briefly describe the significance of the image on the previous page. How does it relate
to this section of the textbook?
Reading Check 26.3 Evolutionary trends in animals
Complete this outline while you read section 26.3 of your textbook, omitting pages
634-635. You do not need to answer in complete sentences.
Scientists believe that animals first appeared in the _______________________
about _____ million years ago.
Tissues and symmetry
The cells of all animals except _______________________ are organized into units called
_______________________. In some simple animals, tissues are not arranged into ____________________.
Body _______________________ refers to how an animal’s body can be divided into similar pieces.
Sponges are _______________________. Animals with _______________________ symmetry have body parts arranged
around a central axis, while animals whose bodies can be divided into mirror-image
halves show _______________________ symmetry. Most bilaterally symmetrical animals show
_______________________, or a concentration of sensory structures and nerves toward the fronts of their bodies.
Body cavities
Animals with bilateral symmetry can be classified according to whether or not they have a fluidfilled space between the body wall and gut. This body cavity is also called a ______________________.
In an _______________________, there is no body cavity. A false coelom, or __________________________,
is filled with a liquid that provides support. _______________________ have a true coelom, which holds
the _______________________ and other internal _______________________.
The coelom cushions protects internal organs from the moving surrounding ______________________.
Segmentation and jointed appendages
Similar repeating units in an animal’s body are called _______________________. Segmentation allows
for greater _______________________ and evolutionary _______________________.
Jointed appendages were first seen in _______________________. Joints permit powerful
_______________________ and help in _______________________.
In the space below, briefly describe the significance of the image above. How does it relate to this section of
the textbook?
Reading Check 26.4 Chordate evolution
Complete this outline while you read 26.4 of your textbook. You do not need to answer in complete
sentences.
Characteristics of chordates
List and describe the four characteristics of all chordates
__________________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
Most chordate species belong to the subphylum _______________________, but there are two other
subphyla in phylum Chordata that do not have a _______________________, and thus are called
_______________________ _______________________. These two types are _______________________ and
_______________________.
The first two traits that allowed fish to become efficient underwater predators were
_______________________ and paired _______________________.
The first vertebrates to emerge on land had _______________________ fins that functioned like
primitive _______________________ and allowed them to move in shallow water. These fishes would
have spent most of their time in the water, and probably represent a _______________________ between animals
that lived only in water and the first vertebrates to live mostly on land, the
_______________________.
Amphibians became better adapted to life on land thanks to _______________________ that could
exchange gases outside of water, a more efficient _______________________ that delivered more
oxygen to the body than a fish’s, and strong _______________________ that supported their bodies and
movement.
Reptiles were even better suited to life on land than amphibians. They developed
_______________________, scale-covered skin and the _______________________ egg. This egg meant
that reptiles were not dependent on _______________________ for reproduction. Today, reptiles,
_______________________ and _______________________ have these kinds of eggs. One important group
of reptiles, the _______________________, dominated life on land for more than 100 million years
before going extinct at the end of the _______________________ Period. _______________________ evolved about
150 million years ago from small dinosaurs.
Early mammals, which first appeared about ____ million years ago, were the size of _______________.
The _______________________ of dinosaurs opened a huge opportunity for the evolution of mammals. Although
mammals tend to be dominant species today, there were even more, larger mammals
that went extinct following the last _______________________ age, about 2 million to 10,000 years ago.