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Chapter 19
Rain Forest Riches
Eukaryotic diversity
• A eukaryote is any
organism of the
domain Eukarya;
eukaryotic cells are
characterized by the
presence of a
membraneenclosed nucleus
and organelles.
Eukaryotic diversity
• The domain Eukarya contains the Plant, Fungi,
and Animal kingdoms, as well as multiple
groups of protists.
Evolution of plant diversity
• A plant is a
multicellular
eukaryote that
has cell walls,
carries out
photosynthesis,
and is adapted
to living on
land.
Evolution of plant diversity
• Land plants first evolved from water-dwelling
algae about 450 million years ago, when life
on earth was confined primarily to the seas.
As plants radiated and diversified on land,
they evolved a number of adaptations that
made them increasingly independent of water.
Evolution of plant diversity
• The earliest plants to make
the transition from water to
land were small, seedless
plants called bryophytes.
Bryophytes lack roots and
tissue for transporting water
and nutrients throughout
their bodies, and therefore
can grow only in damp
environments, where they
can easily absorb water.
Evolution of plant diversity
• Vascular plants
have tissues that
transport water
and nutrients
through the plant
bodies.
Evolution of plant diversity
• The first true vascular
plants were ferns. Like
bryophytes, ferns do not
produce seeds. Ferns can
stand upright and grow tall
because vascular tissue
keeps stems rigid and
transports water and
nutrients from one end of
the plant to the other.
Evolution of plant diversity
• Seed plants first emerged
about 360 million years
ago, during the late
Devonian period. A seed,
which envelopes a plant’s
embryo, is an ideal package
for withstanding harsh
conditions and traveling to
a location where it can
grow into a new plant.
Evolution of plant diversity
• Gymnosperms are
seed-bearing plants
with “naked” seeds
typically held in cones.
– “Gymnos” is Greek
for “naked,” so the
name literally
means “naked
seeds.”
Evolution of plant diversity
• Angiosperms are
seed-bearing
flowering plants
with seeds
typically contained
within a fruit.
– “Angio” is
Greek for
“vessel” or
“container.”
Evolution of animal diversity
• An animal is a eukaryotic, multicellular
organism that obtains nutrients by ingesting
other organisms.
Evolution of animal diversity
• Many features can be used to group and sort
animals. Historically, anatomical and
embryological evidence were relied upon
most, but in recent years it has become more
common to use DNA. It is clear that all
animals descended from the same common
ancestor and diversified into the different
forms we see today.
Evolution of animal diversity
• Early in their history, animals branched into
three main lineages, the legacy of which can
be seen in three distinct animal body plans in
existence today: no symmetry, radial
symmetry, and bilateral symmetry.
Evolution of animal diversity
• The simplest living
animals, such as
sponges, lack
defined tissues or
organs and have an
amorphous shape.
These asymmetrical
organisms are likely
similar to the
earliest animals to
have populated the
oceans.
Evolution of animal diversity
• Animals such as
jellyfish and
corals exhibit
radial symmetry
– the pattern
exhibited by a
body plan that is
circular, with no
clear left or right
sides.
Evolution of animal diversity
• All other animals
exhibit bilateral
symmetry – the
pattern exhibited
by a body plan
with clear right
and left halves
that are mirror
images of each
other.
Evolution of animal diversity
• Bilateral symmetry has become as prevalent
as it is in the animal kingdom because it is a
useful adaptation for seeking out food,
stalking prey, and avoiding predators.
Evolution of animal diversity
• A vertebrate is an animal with a bony or cartilaginous
backbone. While vertebrates are some of the most easily
recognized animals, they are only found on one branch of the
animal tree, the chordates.
Evolution of animal diversity
• Most animals lack a backbone and are
therefore called invertebrates.
Invertebrates
• 95% of animals are invertebrates. A mollusc is
a soft-bodied invertebrate, generally with a
hard shell (which may be tiny, internal, or
absent in some molluscs).
Invertebrates
• An annelid is a segmented worm, such as an
earthworm.
Invertebrates
• Arthropods are the most abundant
invertebrates on earth. An arthropod is an
invertebrate with a segmented body, a hard
exoskeleton, and jointed appendages.
Invertebrates
• An arthropod’s exoskeleton – a hard external
skeleton that covers the body – serves
multiple functions: it protects the organism
from predators, keeps it from drying out, and
affords structure and support for movement,
just as our internal endoskeleton does.
Invertebrates
• The majority of all arthropods are insects – arthropods with three
pairs of jointed legs and a three-part body consisting of head,
thorax, and abdomen.
Vertebrates
• Mammals are a type of vertebrate that have
mammary glands and a body covered with fur.
Fungi
• Fungus (plural: fungi) is a unicellular or
multicellular eukaryotic organism that obtains
nutrients by secreting digestive enzymes onto
organic matter and absorbing the digested
product. By breaking down organic matter
into smaller particles, fungi help release
trapped nutrients.
Fungi
• Fungi are
decomposers –
organisms that
digest and use the
organic molecules
in dead organisms
as sources of
nutrients and
energy.
Fungi
• Multicellular fungi have a body composed of
threadlike structures known as hyphae. Each
individual hypha is a chain of many cells,
capable of absorbing nutrients. Fungal
hyphae interweave to form a spreading mass
known as a mycelium.
Protists
• A protist is a eukaryote that cannot be
classified as a plant, animal, or fungus.
Protists are usually unicellular. Some protists
are similar to animals in that they are
heterotrophic, but because they are
unicellular they are not technically animals.
Protists
• An alga (plural: algae) is a uni- or multicellular
photosynthetic protist. Multicellular algae
share with plants the ability to
photosynthesize, but they differ from plants in
lacking specialized adaptations for living on
land, such as roots, stems, and leaves.
Protists
• The theory of
endosymbiosis: it was
a single-cell protist
that gave rise, some 2
billion years ago, to the
ancestor of all living
eukaryotes.