1
Overview of Animal Diversity
(Chapter 30)
Kingdom Animalia: General Features of Animals
All animals are eukaryotic (Figure 2), multicellular heterotrophs that depend
directly or indirectly on autotrophs (photosynthetic bacteria, plants, and protists
or chemotrophic bacteria and archaeans) for their nourishment.
The animal kingdom (kingdom Animalia) includes about 30 phyla (see Figures 3&4
for the major phyla comprising Animalia) and overall, a tremendous amount of
diversity is exhibited by animals.
While vertebrate species (all of which belong to phylum Chordata) may be the most
commonly thought of animals, almost all living animals (about 99% of all animal
species) are invertebrates (Figure 5; which comprise many phyla).
And so, of the estimated 10 million or so living animal species, only about 42,500
have a backbone (vertebrates).
Most animal phyla are comprised of marine species, with fewer animal phyla
possessing freshwater species, and fewer yet possessing terrestrial species.
Generally speaking, animals have the ability to move and many can do so rapidly and
in complex and well-coordinated ways (Figure 6).
In large part, animals move to reproduce, avoid predators, and locate food.
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Given the great morphological diversity observed in animals, it shouldn’t surprise us
that animals feed in a great many ways.
Nevertheless, the feeding tactics of animals can generally be divided into 5 types:
suspension feeding, deposit feeding, herbivory, predation, and parasitism.
Suspension feeders feed by filtering food from water, air, or a substrate (e.g.,
moist sand) (Figure 7).
Suspension feeders range in size from very small animals (such as rotifers and tiny
shrimp and clams) to extremely large animals (such as baleen whales and basking
sharks; Figure 8), and the structure of the filtering devices used by these animals
can, of course, vary.
Deposit feeders feed by ingesting nutrient rich deposits (such as mud or dirt)
which contain living organisms and other organic matter that can be digested as
food as the deposits pass through the animal’s digestive tract (Figure 9).
Deposit feeding species (such as earthworms) are typically small to medium size
animals and are often worm-like regarding their general habitus (body form).
Herbivores feed on primary producers such as algae or plants (Figure 10).
Like suspension feeders, herbivores range in size from small (e.g., many insects) to
large (e.g., elephants) species.
Herbivory typically requires body structures that can be used to bite, scrape, or
grind plant material, and often herbivores have mechanisms to further pulverize
the tough ingested plant material.
, 3
Furthermore, because the cellulose walls of plant cells are difficult to digest, many
herbivores rely on mutualistic (see Figure 16) bacteria or protists living in their
digestive tracts to break down ingested plant materials into utilizable compounds.
Predators (Figure 11) selectively prey on other organisms, and even other
predators in some instances.
Their style of finding and obtaining prey can often be used to categorize them as
either “sit-and-wait” predators or “stalk and chase” predators (Figure 11).
Predators can range in size from small species, such as tiny predacious worms that
live between the grains of some marine sands, to large species such as the sperm
whale and giant squid (Figure 12).
Some predators ingest their prey whole.
Other predators have morphological adaptations that allow them to cut (such as
the cookie-cutter shark; Figure 13) and sometimes even chew (such as a lion) their
prey into more manageable pieces before swallowing.
Because animal flesh is easier to digest than plant tissue, predators can efficiently
digest a meal even if it is swallowed in large chunks (e.g., as for example when a
shark swallows an entire seal, Figure 14).
Parasites live in or on other organisms referred to as hosts (Figure 15).
Parasites feed on the host and cause at least some degree of harm to it; however,
parasites don’t necessarily cause disease or kill their hosts.
Thus, parasitism is one of the 3 major forms of symbiosis (symbiosis = when two
organisms live in close association with one another) (Figure 16).
Overview of Animal Diversity
(Chapter 30)
Kingdom Animalia: General Features of Animals
All animals are eukaryotic (Figure 2), multicellular heterotrophs that depend
directly or indirectly on autotrophs (photosynthetic bacteria, plants, and protists
or chemotrophic bacteria and archaeans) for their nourishment.
The animal kingdom (kingdom Animalia) includes about 30 phyla (see Figures 3&4
for the major phyla comprising Animalia) and overall, a tremendous amount of
diversity is exhibited by animals.
While vertebrate species (all of which belong to phylum Chordata) may be the most
commonly thought of animals, almost all living animals (about 99% of all animal
species) are invertebrates (Figure 5; which comprise many phyla).
And so, of the estimated 10 million or so living animal species, only about 42,500
have a backbone (vertebrates).
Most animal phyla are comprised of marine species, with fewer animal phyla
possessing freshwater species, and fewer yet possessing terrestrial species.
Generally speaking, animals have the ability to move and many can do so rapidly and
in complex and well-coordinated ways (Figure 6).
In large part, animals move to reproduce, avoid predators, and locate food.
, 2
Given the great morphological diversity observed in animals, it shouldn’t surprise us
that animals feed in a great many ways.
Nevertheless, the feeding tactics of animals can generally be divided into 5 types:
suspension feeding, deposit feeding, herbivory, predation, and parasitism.
Suspension feeders feed by filtering food from water, air, or a substrate (e.g.,
moist sand) (Figure 7).
Suspension feeders range in size from very small animals (such as rotifers and tiny
shrimp and clams) to extremely large animals (such as baleen whales and basking
sharks; Figure 8), and the structure of the filtering devices used by these animals
can, of course, vary.
Deposit feeders feed by ingesting nutrient rich deposits (such as mud or dirt)
which contain living organisms and other organic matter that can be digested as
food as the deposits pass through the animal’s digestive tract (Figure 9).
Deposit feeding species (such as earthworms) are typically small to medium size
animals and are often worm-like regarding their general habitus (body form).
Herbivores feed on primary producers such as algae or plants (Figure 10).
Like suspension feeders, herbivores range in size from small (e.g., many insects) to
large (e.g., elephants) species.
Herbivory typically requires body structures that can be used to bite, scrape, or
grind plant material, and often herbivores have mechanisms to further pulverize
the tough ingested plant material.
, 3
Furthermore, because the cellulose walls of plant cells are difficult to digest, many
herbivores rely on mutualistic (see Figure 16) bacteria or protists living in their
digestive tracts to break down ingested plant materials into utilizable compounds.
Predators (Figure 11) selectively prey on other organisms, and even other
predators in some instances.
Their style of finding and obtaining prey can often be used to categorize them as
either “sit-and-wait” predators or “stalk and chase” predators (Figure 11).
Predators can range in size from small species, such as tiny predacious worms that
live between the grains of some marine sands, to large species such as the sperm
whale and giant squid (Figure 12).
Some predators ingest their prey whole.
Other predators have morphological adaptations that allow them to cut (such as
the cookie-cutter shark; Figure 13) and sometimes even chew (such as a lion) their
prey into more manageable pieces before swallowing.
Because animal flesh is easier to digest than plant tissue, predators can efficiently
digest a meal even if it is swallowed in large chunks (e.g., as for example when a
shark swallows an entire seal, Figure 14).
Parasites live in or on other organisms referred to as hosts (Figure 15).
Parasites feed on the host and cause at least some degree of harm to it; however,
parasites don’t necessarily cause disease or kill their hosts.
Thus, parasitism is one of the 3 major forms of symbiosis (symbiosis = when two
organisms live in close association with one another) (Figure 16).
