The Invertebrate Cell
• What is a Cell?
– comprise tissues -> organs -> organ systems
• Cell Structure
– protoplasm consists of nucleus & cytoplasm
– cytoplasm also with mitochondria & ribosomesThe Invertebrate Cell
• Nucleus - dense and with own membrane
– contains chromosomes => DNA
– DNA - strands with chains of nucleotides
• order of nucleotides (bases) = genetic code
The Genetic Code
• individual units of DNA = genes
• structural genes
– messenger RNA
• regulatory genes
• sum of all hereditary factors (genes) = genotype
• external expression = phenotype
Invertebrate Reproduction
• For invertebrates which is the most primitive?
– Sexual or asexual reproduction?
• parents contribute 1/2 of genetic material
– GENOME
• gametes -> fertilized egg = zygote
Invertebrate Reproduction
Sexual Reproduction (continued)
• from zygote to organism = mitosis
• different cell types = differentiation
• gametes produced by meiosis - reduction division
• Sexual Reproduction = genetic variability
Invertebrate Reproduction
Asexual Reproduction
• reappears in multicellular groups
• can be as simple as mitosis, or complex cell division
• regeneration
• budding => colonial organisms
• Parthanogenesis - clones
• alternation of generations - reproduction type - environment
Adult Body Plans and Cellular Grade
• Unicellular grade
– protozoans
• Primitive multicellular grade
– lack true tissues and organs
– Parazoa => sponges
• Diploblastic grade - 2 tissue layers
– ectoderm and endoderm - mesogloea
– Cnidarians
Adult Body Plans and Cellular Grade
• Triploblastic acoelomate grade - 3 tissue layers
– ectoderm and endoderm + mesoderm
– no body cavity => certain types of worms
• Triploblastic acoelomate grade - 3 tissue layers
– ectoderm and endoderm + mesoderm
– no body cavity => certain types of worms
• Triploblastic coelomate grade and body plan
– coelom = true body cavity
Adult Body Plans and Cellular Grade
• Oligomerous coelomates
– body cavity divided into two or three regions
– depending on function
• Lophophore, gill slits, water vascular system
Developmental Patterns & Ancestry
Patterns - pathways and ancestry
• early cell division = cleavage
– radial versus spiral
• early cell division - which opening appears first
• protostomes versus dueterostomes