Word Roots

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Word Roots

• arch- ancient, beginning (archenteron the
  endoderm-lined cavity, formed during the
  gastrulation process, that develops into the
  digestive tract of an animal)
• blast- bud, sprout -pore a passage
  (blastopore the opening of the archenteron in
  the gastrula that develops into the mouth in
  protostomes and the anus in deuterostomes)
• blasto- produce -cyst sac, bladder
  (blastocyst a hollow ball of cells produced one
  week after fertilization in humans)
• contra- against (contraception the prevention
  of pregnancy)
• -ectomy cut out (vasectomy the cutting of each
  vas deferens to prevent sperm from entering the
  urethra)
• endo- inside (endometrium the inner lining of
  the uterus, which is richly supplied with blood
  vessels)
• epi- above, over (epididymis a coiled tubule
  located adjacent to the testes where sperm are
  stored)

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• extra- beyond (extraembryonic membrane four
  membranes that support the developing embryo in
  reptiles, birds, and mammals)
• fertil- fruitful (fertilization the union of
  haploid gametes to produce a diploid zygote)
• gastro- stomach, belly (gastrulation the
  formation of a gastrula from a blastula)
• labi- lip major- larger (labia majora a
  pair of thick, fatty ridges that enclose and
  protect the labia minora and vestibule)
• oo- egg -genesis producing (oogenesis the
  process in the ovary that results in the
  production of female gametes)
• soma- a body (somites paired blocks of
  mesoderm just lateral to the notochord of a
  vertebrate embryo)
• tri- three (trimester a three-month period)
• tropho- nourish (trophoblast the outer
  epithelium of the blastocyst, which forms the
  fetal part of the placenta)

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Development

• Characteristics of Animals

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Asexual Reproduction

• Creation of offspring whose genes all come from
  one parent without the fusion of egg and sperm

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Budding

• Splitting off new individuals from existing ones
• Yeast cells, hydra

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Binary Fission

• 1 ? 2 of equal size, w/identical genetic info
  of the parent
• Prokaryotes, algae, bacteria

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Fragmentation

• Breaking of parent body into several pieces
• Must be accompanied by regeneration (regrowth of
  body parts from pieces)
• Can occur if pieces develop into clones or if
  part of body grows back

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Parthenogenesis

• Egg develops in absence of fertilization by sperm
  through mitotic cell division
• Occurs naturally in bees to form male drones
• Artificially in some animals (rabbits, frogs)

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Regeneration

• Ability of certain animals to regrow a missing
  body part
• Sometimes parts of animal grow into complete
  animal (planaria, earthworm, lobster, sea star)
• Similar to vegetative propagation in plants

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Advantages of asexual reproduction

• Isolated organisms can reproduce
• Produce many offspring quickly with no time or
  energy lost in gamete production or fertilization
• Quick expansion of population of animals
  genetically well suited for particular environment

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Disadvantage of asexual reproduction

• Produces genetically uniform population
• If the environment changes and becomes less
  favorable to survival, all individuals may be
  affected equally, and entire population may die
  out

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Sexual Reproduction

• Creation of offspring by fusion of two haploid
  (n) sex cells (gametes) to form a diploid (2n)
  zygote

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Advantage of sexual reproduction

• Increases genetic variability among offspring
  from meiosis and random fertilization
• Provides greater adaptability to changing
  environments
• More costly in energy than asexual
• Increases diversity in population by creating new
  combinations of alleles in offspring

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Fertilization

• Union of sperm and egg to form diploid zygote
• Activates egg by triggering metabolic changes
  that start embryonic development

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3a. Proteins on sperm head bind to receptor
protein molecule
4a. Species-specific protein molecules on surface
binds with specific receptor proteins on
vitelline layer-ensures that sperm of other
species cannot fertilize egg
5a. Fertilization membrane forms
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Fertilization envelope

• No other sperm can enter once membranes fuse
  because plasma membrane becomes impenetrable to
  other sperm cells
• Vitelline layer hardens and separates from plasma
  membrane
• Space becomes filled with water and vitelline
  layer becomes fertilization envelope, another
  barrier impenetrable to sperm

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Embryonic development

• Mitotic cell divisions of zygote and early
  embryo-cleavage divisions
• Rapid mitotic cell division of zygote
• 1-celled embryo (zygote) ? multicellular embryo
• 1st cells (blastomere) result from divisions of a
  fertilized egg cell
• No cell growth, only division of cytoplasm
• Size decreases with cell divisions from 2-, to 4-
  to 8- cell

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Morula

• Solid ball of 16-32 cells
• Cells are compacted
• Individual blastomeres become progressively
  smaller but size of embryo remains same (still no
  embryo growth)

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Morula
Early Bastula
Late Bastula
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Blastula

• Spherical structure produced by cleavage of a
  zygote
• Outer single layer of cells (blastoderm) surround
  fluid-filled cavity (blastocoele)
• First time two cell types are present-differentiat
  ion starts
• First stage where embryo grows in size

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Gastrulation

• As embryo continues to grow, some cells of
  blastula fold inward, forming 2-layered gastrula
• Outer surface-ectoderm
• Eventually form skin, eyes, nervous tissue
• Inner surface-endoderm
• Develop into viscera, including lining of
  digestive tract, respiratory system, lungs

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Early Gastrula
Gastrula
Early Gastrula
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• Opening of indented space (opening of primitive
  digestive tract in an embryo)
• Protostomes-develops into mouth in Nematodes,
  Annelids, Insecta, Crustaceans
• Deuterostomes-develops into anus in Echinoderms,
  Hemichordates, Chordates

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• Development continues until mesoderm formed
• 3rd cell layer to form between other 2
• forms circulatory, reproductive, and digestive
  systems, endocrine glands, muscles, blood, and
  bone

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Animals groups distinguished by germ layers
(embryonic tissue layers)

• One layer-Porifera
• Diploblastic-
• Two tissue layers-endoderm, ectoderm
• Some (Cnidarians)
• Triploblastic-
• Three tissue layers-endoderm, ectoderm, mesoderm
• Others (both protostomes/deuterostomes)

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Symmetryrepetition of parts in animal or plant
in orderly fashion

• Correspondence of body parts, in size, shape, and
  relative position, on opposite sides of dividing
  line or distributed around central point or axis
• Asymmetrical animals-most sponges
• No general body plan or point of symmetry that
  divides body into mirror-image halves
• Radially symmetrical animals-anemones and sea
  stars
• Body parts organized around central point and
  tend to be cylindrical in shape
• Can be cut along any number of lines to get
  halves that are roughly mirror image
• Bilaterally symmetrical animals-humans and fish
• Body parts arranged the same way on both sides
• Can only use 1 line to get halves that are
  roughly mirror images

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Animals are divided by types of body cavity and
its development

• Acoelomates-platyhelminthes
• Lack enclosed body cavity
• Endoderm, mesoderm, and ectoderm

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• Pseudocoelomates-nematodes
• Fluid-filled central cavity that lies between gut
  and mesodermal tissue layers (pseudocoelom)
• Cavity not been considered true coelom, because
• True mesenteries not present-partially lined
• Development in embryo is quite different
• Move more efficiently-acts like watery skeleton
  against which muscles can work

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• True coelomates-most animals
• Fluid-filled body central cavity-coelom
• Internal space that surround digestive tract or
  other internal structures
• Exists within mesoderm
• Gut suspended within it by sheets of
  tissue-mesenteries
• Gives animal flexibility, protects organs from
  external blows, provides space for expansion of
  organs, like stomach

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Summary of Evolutionary Trends
Although echinoderm adults are radial, they are
grouped with bilateral animals because their
larvae are bilaterally symmetrical and they
evolved from bilaterally symmetrical ancestors