Animal diversity
description
Transcript of Animal diversity
Animal Diversity
Extends far beyond humans and other animals we may encounter
The Animal Kingdom
Figure 32.1
Animal are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers
Several characteristics of animals◦ Sufficiently define the group
• Animals are heterotrophs
– That ingest their food
Nutritional Mode
• Animals are multicellular eukaryotes
• Their cells lack cell walls
Cell Structure and Specialization
• Most animals reproduce sexually
– With the diploid stage usually dominating the life cycle
• After a sperm fertilizes an egg
– The zygote undergoes cleavage, leading to the formation of a blastula
• The blastula undergoes gastrulation
– Resulting in the formation of embryonic tissue layers and a gastrula
Reproduction and Development
Early embryonic development in animals
Zygote
Cleavage
Eight-cell stage
Cleavage
Blastula Cross section of blastula
Blastocoel
Blastocoel
Gastrula Gastrulation
Endoderm
Ectoderm
Blastopore
• Early members of the animal fossil record
– Include the Ediacaran fauna
Neoproterozoic Era (1 Billion–524 Million Years Ago)
• The Cambrian explosion
– Marks the earliest fossil appearance of many major groups of living animals
– Is described by several current hypotheses
Paleozoic Era (542–251 Million Years Ago)
• During the Mesozoic era
– Dinosaurs were the dominant terrestrial vertebrates
– Coral reefs emerged, becoming important marine ecological niches for other organisms
Mesozoic Era (251–65.5 Million Years Ago)
• The beginning of this era
– Followed mass extinctions of both terrestrial and marine animals
• Modern mammal orders and insects
– Diversified during the Cenozoic
Cenozoic Era (65.5 Million Years Ago to the Present)
• Animals can be categorized
– According to the symmetry of their bodies, or lack of it
• Some animals have radial symmetry
– Like in a flower potRadial symmetry. The parts of a radial animal, such as a sea anemone (phylum Cnidaria), radiate from the center. Any imaginary slice through the central axis divides the animal into mirror images.
Symmetry
Bilateral symmetry. A bilateral animal, such as a lobster (phylum Arthropoda), has a left side and a right side. Only one imaginary cut divides the animal into mirror-image halves.
Some animals exhibit bilateral symmetryOr two-sided symmetry
• Based on certain features seen in early development
– Many animals can be categorized as having one of two developmental modes: protostome development or deuterostome development
Protostome and Deuterostome Development
In protostome development◦ Cleavage is spiral and determinate
In deuterostome development◦ Cleavage is radial and indeterminate
Cleavage
Protostome development(examples: molluscs, annelids,
arthropods)
Deuterostome development(examples: echinoderms,
chordates)
Eight-cell stage Eight-cell stage
Spiral and determinate Radial and indeterminate
(a) Cleavage. In general, protostomedevelopment begins with spiral, determinate cleavage.Deuterostome development is characterized by radial, indeterminate cleavage.
In protostome development◦The splitting of the initially solid masses of
mesoderm to form the coelomic cavity is called schizocoelous development
In deuterostome development◦Formation of the body cavity is described as
enterocoelous development
Coelom Formation
Figure 32.9b
Archenteron
Blastopore MesodermCoelom
BlastoporeMesoderm
Schizocoelous: solidmasses of mesodermsplit and form coelom
Enterocoelous:folds of archenteronform coelom
Coelom (b) Coelom formation. Coelom formation begins in the gastrula stage. In protostome development, the coelom forms from splits in the mesoderm (schizocoelous development). In deuterostome development, the coelom forms from mesodermal outpocketings of the archenteron (enterocoelous development).
In protostome development◦ The blastopore becomes the mouth
In deuterostome development◦ The blastopore becomes the anus
Fate of the Blastopore
Figure 32.9c
Anus
Anus
Mouth
Mouth
Mouth developsfrom blastopore
Anus developsfrom blastopore
Digestive tube