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Biology 30 - Ch. 22 – Animal Development Notes
Animal Development
 Animal development begins with the process of ________________________.
 Fertilization is the union of __________________ to produce a ____________.
Several steps are required to accomplish this union.
 ____________________________________
 The sperm must ____________________________________ of the ovum
 The ovum must prevent more ___________________________________________
 Animal growth and development also involves the ___________________ of cells.
 Until cells differentiate into the many tissues and organs in an organism they are
_____________________. Identical cells that have the potential to be anything are
described as being __________________.
 Totipotent cells are commonly called ________________. ______________ may
develop into any one of the hundreds of different tissues in our body.
 All cells in the early embryo are totipotent up until the _______________ or so.
 Stem cells require a signal to tell them what to become. The use of stem cells in
medical research has some fascinating applications. However, many ethical questions
arise when using early embryo stem cells for research and clinical studies.
Stages of the Growing Embryo - Embryology
 The study of the growing embryo is a fascinating topic. The single fertilized ovum
slowly forms into a ball of cells that begins to differentiate into the 3 embryonic germ
layers called the ___________________________. As it transforms it passes through
several stages including the following:
 ___________________ - fertilized ovum
 ___________________ - hollow ball of cells
 ___________________ - implantation into uterine wall
 ___________________ - formation of germ layers
 ___________________ - nervous tissue formed
 Upon formation of the spinal cord and brain during neurulation, rapid growth of
tissues and organs begins. The human is referred to as an ____________ once it has
implanted as a ____________. It is called a __________ 8 weeks after conception
until birth.
Pre-Implantation
 ______________ - the growing embryo begins with fertilization.
 in this image you can see the nuclei of the ovum and sperm cell about to unite
 at the moment the nuclei unite conception is said to have occurred
 the woman is not yet pregnant, this is only after implantation
2 - Cell Stage – Cell begins process of ________________.
 the zygote divides by _____________ to create two identical cells
 the cells are ____________________ and do not grow during the rapid mitotic
divisions
 each cell is totipotent, having total potential to be any _________________________
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Biology 30 - Ch. 22 – Animal Development Notes
4-Cell Stage - The cells continue to divide by _____________ creating 4 identical cells.
 The cells have not ____________________________.
8-Cell Stage - the cells continue to divide by _____________ creating 8 identical cells
Morula - a _________________________________
 morula in Latin means blackberry or raspberry
 like the 2, 4, and 8 cell stages the cells are totipotent
Blastula
 The morula eventually creates a ______________ of itself called the _____________
 The space inside of the blastula is called the _____________________
 It is within this space that the _____________________________________
 The blastocoel forms the ___________________________________
 The blastula is still free within the female's body but will soon implant in the uterus
Blastocyst
 The blastocyst is _______________________ from its shell.
 As the hatching proceeds the blastula will implant into the _____________________.
The ____________________ forms and the embryo is nourished by its mother.
Implantation
 Implantation of the blastula occurs in the upper third of the ______________.
Post-Implantation
 Following implantation the embryo _____________________.
 Tissues, organs and organ systems begin forming in a process called _____________.
 The three embryonic germ layers responsible for differentiation form postimplantation
Gastrulation
 During gastrula formation the ________________________ form
 _____________ forms tissues associated with outer layers: skin, hair, sweat glands,
epithelium. The brain and nervous system also develop from the ectoderm.
 The _______________ forms structures associated with movement and support: body
muscles, cartilage, bone, blood, and all other connective tissues. Reproductive system
organs and kidneys form from mesoderm.
 The _________________ forms tissues and organs associated with the digestive and
respiratory systems.
 Many endocrine structures, such as the thyroid and parathyroid glands, are formed by
the endoderm. The liver, pancreas, and gall bladder arise from endoderm.
 The _______________is the opening to the digestive system that will develop into the
_______.
External and Internal Development
 Embryonic development can occur inside or outside the female body.
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Biology 30 - Ch. 22 – Animal Development Notes
 No matter where development takes place there are certain conditions that must be
met for development.
 These include _________________________________________________________
__________________________________________________.
External Development
 There are 2 places where this can occur; in water or on land.
 In most aquatic animals, there is vey little ____________________ for the young.
 Some do care for their young, but most produce large numbers of young in the hopes
that a few will survive to adulthood.
 On land, fertilization takes place inside the female body followed by development
outside the body.
 In terrestrial animals, the embryo is generally _______________________________.
 Inside the egg the developing embryo is contained within a __________ environment.
The shell is ______________________________________________________.
 The shell can be leathery as in reptiles or hard as in birds.
 The egg is a self contained environment that has everything the embryo needs for
development.
Parts of the Egg
 _____________________: Its primary purpose is to protect the egg yolk and provide
additional nutrition for the growth of the embryo. It is contains many proteins.
 ______________: Gives air for the embryo to breathe just prior to hatching.
 ________________: Membrane that surrounds the embryo and yolk sac.
 ________________: Fluid filled sac that cushions the embryo.
 ________________: Contains stored food for the embryo.
 ________________: Holds wastes produced by the embryo.
Internal Development
Placental Mammals
 All bear live young, which are nourished before birth in the mother's uterus through a
specialized embryonic organ attached to the uterus wall, the _______________.
 The ____________________________ period varies from 16 days for a hamster to
624 days for an Indian Elephant
 The embryo is nourished from the blood of the mother through the ______________.
The blood of the mother and the fetus ______________________________________.
Non Placental Mammals
 Give birth very early and the young animal climbs from the mother's birth canal to the
pouch. The young embryo attaches to a nipple and finishes development in the pouch.
 Very common in Australia and surrounding islands. The only marsupial outside of
Australia is the American Opossum.
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