Lecture 4 MARB 435Outline of Last Lecture1. Introduction to Protists2. Introduction to Protozoan’s3. Eukaryotic Cell Componentsa. Cell Components & Function4. Cytoskeleton5. Flagella & Cilia6. Pseudopodiaa. Protozoan Specialized Parts7. Introduction to Protozoan Groupsa. Alveolatesi. Phylum Ciliophoraii. Phylum Dinoza (Din flagellates)1. Noctiluca scintillans2. Pfiesteria piscicid3. Human Concerns of Dinoflagellates4. Karenia breve5. Hematodinium perezi6. Zooanthellaeiii. Phylum Apicomplexa1. Malariab. Amoebozoac. Rhizariai. Phylum Radiozaii. Phylum Formaniferad. Excavatai. ChoanoflagellatesOutline of Current Lecture1. Introduction to Metazoaa. Metazoan tissuesb. Extracellular Matrix (ECM)c. Intercellular junctions2. Origin of Metazoa3. Embryology4. Important Terminology5. Introduction to Zooplanktona. Life in the water column6. Types of Planktona. Mesozooplanktonb. Macrozooplanktonc. Megazooplankton7. Temporary and Permanent Zooplankton8. Planktonic Larvaea. Pros & Cons of Larvae9. Metamorphosis10. Challenges of Planktonic Life11. Defenses from Predation12. FeedingCurrent Lecture DescriptionIn today’s lecture, the notes consist of discussing the group of Metazoa and their origin.The notes discuss their tissue type and components. The notes also being the introduction ofPlankton and the various types with definition and examples.Introduction to MetazoaMetazoa commonly known as Animalia and are multicellular organisms. Protozoanswere initially recognized as animals but once scientists concluded there polyphyletic ancestrymaking them no longer classified as a true kingdom. Polyphyletic means there are multiplelineages and there is not one common ancestor. The sister group to Metazoa arechoanoflagellates.Metazoan TissuesMetazoan cells are commonly organized by their tissue layers. They have two maintissue layers, epithelial and connective. Epithelial tissues are tissues a layer of connecting cellscovering the body or inner lining of a cavity. The epithelial cells secrete a basal lamina which isconnected by intercellular junctions. Connective tissue is a tissue with widely spreaded cellsthat don’t actually connect. These cells are in the extracellular matrix (ECM). The PhylumPorifera (Sponges) and Placozoa don’t contain epithelial tissue. The Metazoan tissue is made ofmany parts such as the apical surface, cuticle, epidermia, basal lamina, extracellular matrix(ECM), Basal surface and the connective tissue.- Apical surface of the epithelium- The upper most layer of a Metazoan which hasmicrovilli which are like pseudopodia and flagella which assist with locomotion.- Cuticle- Is a part of the extracellular matrix (ECM).- Epidermia- Epithelial tissue that covers the body.- Basal Lamina- A thin layer of the ECM secreted by the epithelial cells.- Extracellular Matrix (ECM) - The layer beneath the Basal surface containing collagen.- Connective tissue- Tissue layer with separated cells inside the ECM.- Basal surface- Surface of the epithelium.Extracellular Matrix (ECM)The ECM is a complex network of proteins and polysaccharides such as collagen.Collagen is one of the main proteins found in connective tissue. The ECM’s function is tosupport the cell and help it maintain its shape and structure. The ECM is very importantwhen it comes to cell and tissue development and physiology. Collagen is a fibrous proteinthat’s unique to metazoans. They form a triple helix with polysaccharide forming animportant component of skin and bone.Intercellular JunctionsIntercellular Junction is a part of the epithelial tissue. They are commonly defined byeither being gap or belt junctions. Gap junctions are directly connected to the cytoplasmand adjacent cells. The cell membrane around one cell has a small amount of spacebetween it and the adjacent cell. Gap junction’s main function is to ensure that adjacentcells are able to communicate with one another. This space is so small is can be measured innanometers. These small spaces only allow small particles to go through them, so proteinsare unable to travel between these gap junctions. Another type of junction is belt junctionsunlike gap junctions which are located on the lower region of a cell; belt junctions are nearthe top part of the cell. Belt junctions are ‘tight junctions’ and act as a barrier for diffusionfor proteins and lipids. They also act as a seal between adjacent cells. Another intercellularjunction is hemidesmosome. Hemidesmosome has a function to connect a cell to the ECMusing adhesion proteins. Desmosome are dense plaques of protein acting as anchors forintermediate cell cytoplasm filaments.Origin of MetazoaMetazoans where introduced earlier in the notes, but their origin can be traced back totwo theories, the colonial and syncytial theory. The original theory states that Metazoa derivedfrom flagellated Protzoa that were in colonies. The original theory is supported by molecularand morphological data which is introduced in lecture one notes. The syncytial theory believesthat Metazoa derived from a multinucleate and unicellular organism called a syncytium.Syncytium is a large cell with multiple nuclei.EmbryologyEmbryology is the study of the way cells develop and reproduce. There’s terminology thestudent must first understand before studying embryology such as cleavage, gastrulation andgerm layers. Cleavage is the process where cells begin to separate and form new cells duringreproduction. Gastrulation is the process where germ layers begin to develop. Germ layer is thethree layers that line within the organism. Metazoans undergo various steps duringreproduction. The first step is when two haploid cells combine to make a zygote next is cleavagewhere the cell divides without growth. This step makes the zygote develop into the blastula. Theblastula is simply what the embryo is called when it’s in the early stages of development. Thenthe process of gastrulation begins and this is where the germ layers begin forming. The germlayers are the endoderm, mesoderm, and ectoderm. The endoderm lines the inner part of theorganism; the mesoderm separates the endoderm and ectoderm. The ectoderm is known as theouter germ layer.Important TerminologyEggs- Animal Pole- Zygote surface that the nucleus is closest to.-