BISC 1112 Lecture Notes - Lecture 7: Human Embryogenesis, Blastomere, Blastula
28 Aug 2016
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Diversity of Life 2
Chapter 32: An Overview of Animal
Diversity
32.1: Animals are multicellular, heterotrophic eukaryotes with
tissues that develop from embryonic layers
-Nutritional Mode
•animals differ from both plants and fungi in their mode of nutrition
-plants are autotrophic eukaryotes
capable of generating organic
molecules through photosynthesis
-fungi are heterotrophs that grow on
or near they food
•feed by absorption (often after
they have released enzymes that
digest the food outside their
bodies)
-animals cannot construct all of their
own organic molecules
•most cases they ingest them—
either by eating other living
organisms or by eating nonliving
organic material
•most feed by ingesting their food
and then using enzymes to digest it
within their bodies
-Cell Structure and Specialization
•animals are eukaryotes and multicellular
-lack the structural support of cell
walls
•instead, proteins external to the
cell membrane provide structural
support to animal cells and connect
them to one another
-most abundant of thee proteins
is collagen (not found in plants or
fungi)
-cells of most are organized in tissues
(groups of similar cells that act as a
functional unit)
•example: muscle tissue and nervous
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tissue are responsible for moving the body and conducting nerve impulses
-Reproduction and Development
•most animals reproduce sexually, and diploid stage usually dominates the life cycle
-in most, a small, flagellated sperm fertile a larger, nonmotile egg, forming a diploid zygote
•zygote then undergoes cleavage (succession of mitotic cell divisions without cell growth
between the divisions)
-cleavage leads to the formation of a blastula (hollow ball of cells that marks the end of
the cleavage stage during early embryonic development in animals)
•following this is gastrulation (process during which the layers of embryonic tissues
that will develop into adult body parts are produced)
-resulting developmental stage is called a gastrula
-life cycles of most animals include at least one larval stage
•larva
-sexually immature form of an animal that is morphologically distinct from the adult
-usually eats different food
-may even have a different habitat than the adult
-eventually undergo metamorphosis (developmental transformation that turns the animal
into a juvenile that resembles an adult but is not yet sexually mature)
-all animals have developmental genes that regulate the expression of other genes, and many of
these regulatory genes contain sets of DNA sequences called homeoboxes
•most animals share a unique homeobox-containing family of genes known as Hox genes
•Hox genes
-play important roles in the development of animal embryos, controlling the expression of
many other genes that influence morphology
-in most animals, these genes regulate the formation of the anterior-posterior axis
32.2: The history of animals spans more than half a billion years
-Steps in the Origin of Multicellular Animals
•scientists exploring how animals may have arisen from their single-celled ancestry have noted
that the origin of multicellularity requires the evolution of new ways for cells to adhere and
signal to each other
-Neoproterozoic Era (1 Billion-542Million Years Ago)
•Ediacaran biota
-first fossils of animals dated from about 560 million years ago
-soft-bodied multicellular eukaryotes
-named from the Edicara Hills of Australia where fossils of these organisms were first
discovered
-Paleozoic Era (542-251 Million Years Ago)
-Cambrian explosion
•phenomenon occurred during the Paleozoic era
•strata that are 535-525 million years old, paleontologists have found the oldest fossils of
about half of all extant animal phyla
•Vertebrates (fishes) emerged as the top predator of the marine food web
•Arthropods were the first animals to adapt to terrestrial habitats
•two vertebrates survive today: the amphibians (frogs and salamanders) and the amniotes
(reptiles, including birds and mammals)
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Document Summary
32. 1: animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers. Nutritional mode: animals differ from both plants and fungi in their mode of nutrition. Plants are autotrophic eukaryotes capable of generating organic molecules through photosynthesis. Fungi are heterotrophs that grow on or near they food: feed by absorption (often after they have released enzymes that digest the food outside their bodies) Cell structure and specialization: animals are eukaryotes and multicellular. Lack the structural support of cell walls: instead, proteins external to the cell membrane provide structural support to animal cells and connect them to one another. Most abundant of thee proteins is collagen (not found in plants or fungi) Cells of most are organized in tissues (groups of similar cells that act as a functional unit: example: muscle tissue and nervous tissue are responsible for moving the body and conducting nerve impulses. Reproduction and development: most animals reproduce sexually, and diploid stage usually dominates the life cycle.
