2. 26 – 1 Introduction to the
Animal Kingdom
• Of all the kingdoms of organisms,
the animal kingdom is the most
diverse in appearance
3. What Is an Animal?
• Animals are Multicelular
• Animals are Eukaryotic heterotrophs
• Animal cells lack cell walls
• Animals belong to the kingdom Animalia
• The bodies of most animals contain tissues
• Ex.)epithelial, connective tissue (bone,
blood) nervous tissue
• Animals are informally grouped into 2
categories
4. Invertebrates
• Animals that don’t have a
backbone
• Over 95% percent of all animal
species are grouped into this
category
28. Trends in Animal Evolution
• Complex animals tend to have
high levels of cell specialization
and internal body organization,
bilateral body symmetry, a front
end or head with sense organs
and a body cavity
29. Cell Specialization and Levels of
Organization
• As animals evolved, their cells
have become specialized to carry
out different functions
• Ex.) Movement, digestion,
nervous system
30. • Large animals need greater
efficiency in body processes than
smaller animals
• Groups of specialized cells form
tissues, which join together to
form organs and organ system -
all of which work together to carry
out a variety of complex functions
38. Cephalization
• Concentration of sense organs
and nerve cells at the front of an
animals body
• Organisms with cephalization can
respond to the environment in
more sophisticated ways than can
simpler organisms
39.
40. Body Cavity Formation
• Most animals have a body cavity which is
a fluid filled space that lies between the
digestive tract and the body wall
• A body cavity is important because it
provides a space in which internal organs
can be suspended so that they are not
pressed on by muscle or twisted out of
shape by body movements
• Body cavities also allow for specialized
regions to develop, and they provide room
for internal organs to grow and expand
41. Adaptive Radiation
• Over the course of evolution, the
appearance of new adaptations –
such as jaws and paired
appendages – has launched
adaptive radiations in chordate
groups
43. Convergent Evolution
• Adaptive radiations sometimes
produce species that are similar in
appearance and behavior, even
though they are not closely
related. This trend is called
convergent evolution
118. Chordate Traits
• Dorsal notochord at some time
• Pharyngeal gill slits (or pouches)
at some time
• Dorsal hollow nerve cord at some
time
• Bilateral symmetry
119. Chordate Traits
• Tissues and organs of vertebrates
– Backbone
– Brain and nervous system
– Closed circulatory system
– Complete digestive tract
– Paired kidneys
– Gills or lungs
– Paired image forming eyes
• Sexual reproduction (separate sexes)