Download Chapter 27 Introduction to Animals Chapter 27 Section 1

Chapter 27 Introduction to Animals
Chapter 27 Section 1: Characteristics of Animals
General Features of Animals
Number of known animals = Over one millio n species
Common features all animals share:
1. Heterotrophy
Animals are heterotrophs
They cannot make their own food = Must eat other organisms.
2. Mobilit y
Animals can perform rapid co mplex movements.
They mo ve by muscle contraction or shortening.
What are some ways animals move?
3. Mult icellarit y
Animals have more than one cell
4. Diplo idy
Chro mosomes are in pairs.
One set fro m the mother and one set from the father.
Advantage = new gene combinat ions which give rise to variet y.
5. Sexual Reproduction
Almost all animals reproduce sexually by producing gametes (sex cells).
Our sex cells or gametes are eggs (female) and sperm (male).
6. Absence of cell wall
Allows for mobilit y.
7. Blastula formation
Fertilized egg develops
into a hollow ball of
cells wit h 3 primary
tissue layers.
8. Tissues
All animals except sponges have cells arranged into tissues.
Body Symmetry
Refers to an animal’s body plan
Asymmetrical – irregular in shape
Radial symmetry – body parts arranged around central axis.
Bilateral symmetry – body design in which there are distinct right and left halves
o Cephalizat ion – anterior concentration of sensory structures and nerves (brain)
Internal Body Cavity
Bilaterally symmetric animals have 1 of 3 basic body plans.
o Acoelo mates have no body cavit y or coelo m.
o Pseudocoelo mates have a body cavit y lo cated between the mesoderm and the endoderm.
o Coelo mates have a body cavit y located ent irely wit hin the mesoderm.
Body Segmentation
Segmented animals are composed of a series of repeating, similar unit s called segments. Ex:
earthworm
Crustaceans, spiders and insects show some degree of segmentation, but it may be hard to see in
the adult stage.
Vertebrates (animals wit h a backbone) do not show segments externally, but there is evidence of
segmentation in a vertebrate embryo.
Advantages of segmentation:
o Great flexibilit y and mo bilit y
o Since each segment repeats many o f the organs in the adjacent segment, an injured animal
can st ill perform vital funct ions.
o Offers evo lut ionary flexibilit y
Kinds of Animals
Kingdo m Anima lia (us)
o 35 major divis io ns called phyla (singular: phylum)
o A phylogenet ic tree visually represents the relat ionships among various groups of animals
based on:

Fossil record

Comparing the anatomy & physio logy o f animals

Comparing DNA in the genes
o The animal kingdo m is divided into 2 groups

Invertebrates (animals wit hout a backbone)

Vertebrates (animals wit h a backbone)
Chapter 27 Section 2: Animal Body Systems
Tissues and Organs
Tissues - A group of similar cells that work together to perform a specific funct ion.
Organ - Two or more types of t issues working together to perform a specific function
Body Systems
Digestion
o Single celled organisms and sponges digest their food within their body cells.
o In simpler animals, there is only one opening called a gastrovascular cavit y.
o Animals, such as us, have a digest ive tract with 2 openings: a mouth and an anus.

This is a one-way flow, allowing cells to perform specific funct ions.
Respiration
o In simple animals, oxygen and carbon dioxide are exchanged direct ly with the environment
by diffusio n.
o Larger, more complex animals, have specialized respiratory structures (lungs).
o Some aquat ic (and a few terrestrial) animals breath through gills.
Circulat ion
o In simple animals, their cells are exposed to the environment or gastrovascular cavit y to
obtain oxygen and nourishment.
o Two types of circulatory systems:
1. Open circulatory system – heart pumps fluids through vessels into a body cavit y,
bathing the tissues. The fluid co llects in open spaces and flows back to the heart.
2. Closed circulatory system – heart pumps blood through a system of blood vessels
Nerve Impulses
o Nerve cells (neurons) are specialized for carrying messages in the form o f electrical
impulses (conduction).

Coordinate the body act ivit ies, allowing the animal to sense and respond.
Support
o Skeleton

Hydrostatic skeleton – consists of water contained under pressure in a closed cavit y.
Ex: hydra and earthworms

Exoskeleton – rigid external (outer) skeleton that encases the body of an animal.
Ex: insects

Endoskeleton – hard material, such as bone, inside an animal (us).
Excretion
o Removal o f wastes produced by cellular metabo lis m.
Reproduction
Asexual – does not invo lve the fusio n (unio n) of 2 gametes.
o Fragmentation – piece of body fragments (breaks off) and the fragment grows into a new
organism.
o Parthenogenesis – new individual develops from an unfert ilized egg (bees).
Sexual – new individual is formed fro m the unio n of male and female sex cells
o Testes produce male gametes (sperm).
o Ovaries produce female gametes (eggs or ova)
o Hermaphrodites – have both testes and ovaries. But the eggs and sperm are produced at
different times, so self-fertilizat ion does not occur.
o External fertilizat ion – occurs in most aquatic animals. Sperm and eggs are released near
one another in water, where fertilization occurs.
o Internal fertilizat ion – the unio n of sperm and egg occurs within the female’s body.
Chapter 37 Introduction to Body Structure
Section 1: Body Organization
Levels of Cellular Organization
o Human body contains more than 100 trillio n cells and more than 100 kinds of cells!
o Levels of organizat ion: Cells → Tissues → Organs → Organ Systems → Organism
Four Kinds o f Tissues
o Epithelial t issue:

Covers the body and lines most body cavit ies

Protects from dehydrat ion and phys ical damage
o Nervous tissue

Nerve cells (neurons) and their supporting cells

Carry information throughout the body
o Connective tissue

Support, protect and insulate the body

Includes fat, cartilage, bone, tendons and blood
o Muscle tissue 3 kinds that enable mo vement of body structures by muscle contraction.
1. Skeletal muscle – vo luntary (you consciously control it); moves bones
2. Smooth muscle – involuntary (you cannot consciously control it); lines blood vessels
and ho llow organs; slow lo ng-last ing contractions
3. Cardiac muscles – invo luntary and found in the heart; pumps blood.
Stem Cells
o Embryo nic stem cells are immortal (divide indefinitely) and have the potential to develop into
any t ype of cell. They o ffer the possibilit y o f repairing damaged tissue.
o Adult stem cells are not as versat ile and are not immortal (most stop reproducing after fewer
than 100 cell divis io ns).
Organ Systems
Body organs consist of two or more types of tissues working together to perform a specific
funct ion.
Organ systems consist of different organs working together to perform a specific function.
o Circulatory – transports nutrients, wastes, hormones & gases
o Digestive – extracts and absorbs nutrients from food, removes wastes and maintains water and
chemical balances.
o Endocrine – regulates body temperature, metabo lism, development and reproduction,
maintains ho meostasis and regulates other organ systems.
o Excretory – removes wastes fro m blood and regulates the concentration of body fluids.
o Immune – defends against pathogens and disease
o Integumentary – (skin) – protects against injury, infect ion and fluid loss and helps regulate
body temperature.
o Muscular – Moves limbs and trunk and substances through the body and provides structure and
support.
o Nervous – regulates behavior, maintains ho meostasis, regulates other organ systems and
controls sensory and motor funct ions.
o Reproductive – produces gametes and offspring.
o Respiratory – moves air into and out of the lungs and controls gas exchange between the blood
and the lungs.
o Skeletal – protects and supports the body and its organs, interacts with skeletal muscles to
provide movement, and produces red and white blood cells and platelets.
Body Cavit ies – house and protect major organs
Thoracic – contains the heart and lungs
Cranial – contains the brain
Abdo minal – contains the digest ive organs (stomach, gall bladder, liver, pancreas)
Spinal – down center of back, ho lds spinal cord and nerves
Endothermy
•
Humans are endotherms, like all mammals.
•
Humans maintain a temperature of 37◦C (98.6◦F)
•
The human body uses a great deal of energy to maintain a stable internal condit ion.