Transcript Chapter 19
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.