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Lecture

bioa02 chapter 31


Department
Biological Sciences
Course Code
BIOA02H3
Professor
Mary Olaveson

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Chapter 31
31.1 – What evidence indicate the animals are monophyletic?
-What traits distinguish the animals from the other groups of organisms?
oAll animals are multicellular
oAnimal life cycles feature complex patter of development from a single-
celled zygote into a multicellular adult
oAll animals are heterotroph  able to synthesized very few organic
molecules from inorganic chemicals, therefore have to take nutrients
oAnimals use internal processes to break down materials form their
environment into the organic molecules they need most
oMost animals can move
-animals share a common ancestor comes form their many shared derived
molecular and morphological traits
omany gene sequences support the monphyly of animals
othey display similarities in the organization and function of their Hox
genes
othey have unique types of junctions between their cells
ohave common set of extrecelluar matrix molecules  collagen, and
proteoglycan
-the ancestor of animal is most likely to be a colonial flagellated protest
-once functional specialization had began, cells continued to differentiate
-clues to the evolutionary relationships among animal groups can be found in
fossils, in patterns of embryonic development, in the morphology and physiology
of living animals, in the structure of animal molecules, and in the genomes of
animals
-the first few cell divisions of a zygote are known as cleavage  the number of
cells in the embryo doubles with each cleavage
-a number of different cleavage patterns exist among animals  they are
influenced by the configuration of the yolk, the nutritive material that nourishes
the growing embryo
-radical cleavage  with the fertilized egg cell dividing in an even pattern
ois the ancestral condition for eumetazoans, so it is found among
protostomes and diploblastic animals
-spiral cleavage  a complicated derived permutation of redial cleavage
ois found among many lophotrochozoans, such as earthworms and clams
-the early branches of the exdysozoans have radial cleavages, although most
doesn’t have either radial or spiral cleavage
-the embryos of diploblastic animals have only two of these cell layers  an outer
ectoderm and an inner endoderm
-the embryo of triploblastic animals have  ectoderm, endoderm, and mesoderm,
which lies between the ectoderm and the endoderm
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-dueing the early development in many animals, a hollow ball one cell think
indents to form a cup-shaped structure  gastrulation
othe opening of the cavity formed by this indentation  blastopore
-the pattern of development after formation of the blastopore has been used to
divide the tripoblastic into two groups
oprotostomes  the mouth arises from the blastopore; the anus forms later
odeuterostomes  blastopore beomces the anus, the mouth forms later
31.2 – what are the features of animal body plans?
-body plan  the general structure of an animal, the arrangement of its organ
systems, and the integrated functioning of its parts
-have four key features:
othe symmetry of the body
othe structure of the body cavity
othe segmentation of the body
oexternal appendage that move the body
-symmetry  animal said to be symmetrical
-spherical symmetry  the simplest form of symmetry, in which body parts
radiate out form a central point
ohave infinite planes to divide the organism into similar halves
owidespread among unicellular protests
-radial symmetry  there is one main axis around which body parts are arranged
octenophores and cnidarians are composed primarily of radial symmetry
omany radial symmetrical animals are sessile (sedentary)
ocan move equally well in any direction
-bilateral symmetry  is characteristic of animals that move in one direction
ocan be divided into mirror-image (left and right) halves by a single plane
othis plane runs from the tip (anterior) to its tail (posterior)
oa plane at right angles to the midline divides the body into two dissimilar
sides
the back of a bilaterally symmetrical animal is its dorsal surface
the belly, which contains them mouth, is its central surface
oit is strongly correlated with cephalization  is the concentration of
sensory organs and nervous tissues in a head at the anterior end
-the structure of the body cavity strongly influences the ways in which it can move
-acoelomate  animals such as flatworms lack an enclosed, fluid-filled body
cavity
othe space between the gut (endoderm) and the muscular body wall
(mesoderm) is filled with cells  mesenchyme
-pseudocoelomate  animals have a body cavity  pseudocoel, a fluid-filled
spaced in which many of the internal organs are suspended
opseudocoel is enclosed by muscles (mesoderm) on its outside
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ono inner layer of mesoderm surrounding the internal organs
-coelomate  animals have a coelom  that develops within the mesoderm
oit is lined with a later of muscular tissue  peritoneum, which also
surrounds the internal organs
othe coelom is enclosed on both the inside and the outside by mesoderm
-the body cavities of many animals function as hydrostatic skeleton
owhen the muscles surrounding them contract, they move to another part of
the cavity
oan animal with both circular muscle (encircling the body cavity) and
longitudinal muscles (running along the length of the body) has even
greater control over its movement
-segmentation  facilitates specialization of different body regions
oallows an animal to alter the shape of its body in complex ways and to
control its movements precisely
omuscles in each individual segment can change the shape of that segment
independently of the others
oin some animals, segments are not apparent externally
oin other animals, such as the annelids, similar body segments are repeated
many times
oin yet another animal, including most arthropods, the segments are visible
but differ strikingly
-appendages that project externally from the body greatly enhance an animal’s
ability to move around
31.3 – how do animals get their food?
-although there are many animals that rely on photosynthetic endosymbionts for
nutrition, most animals must actively obtain an outside source of nutrition  food
-to acquire food, animals must expend energy, either to move through the
environment to where food is located or to move the environment and the food it
contains to them
-Motile  animals that can move from one place to another
-Sessile  animals that stay in one place
-Feeding strategies
oFilter feeders  capture small organisms delivered to them by the
environment
oHerbivores  eat plants or parts of plants
oPredators  capture and eat other animals
oParasites  live in or on other organisms from which they obtain energy
and nutrients
oDetritivores  actively feed on dead organic materials
-Individuals of some animals employ more than one feeding strategy
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