Lecture 4 MARB 435 Outline of Last Lecture 1 Introduction to Protists 2 Introduction to Protozoan s 3 Eukaryotic Cell Components a Cell Components Function 4 Cytoskeleton 5 Flagella Cilia 6 Pseudopodia a Protozoan Specialized Parts 7 Introduction to Protozoan Groups a Alveolates i Phylum Ciliophora ii Phylum Dinoza Din flagellates 1 Noctiluca scintillans 2 Pfiesteria piscicid 3 Human Concerns of Dinoflagellates 4 Karenia breve 5 Hematodinium perezi 6 Zooanthellae iii Phylum Apicomplexa 1 Malaria b Amoebozoa c Rhizaria i Phylum Radioza ii Phylum Formanifera d Excavata i Choanoflagellates Outline of Current Lecture 1 Introduction to Metazoa a Metazoan tissues b Extracellular Matrix ECM c Intercellular junctions 2 Origin of Metazoa 3 Embryology 4 Important Terminology 5 Introduction to Zooplankton a Life in the water column 6 Types of Plankton a Mesozooplankton b Macrozooplankton c Megazooplankton 7 Temporary and Permanent Zooplankton 8 Planktonic Larvae a Pros Cons of Larvae 9 Metamorphosis 10 Challenges of Planktonic Life 11 Defenses from Predation 12 Feeding Current Lecture Description In 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 of Plankton and the various types with definition and examples Introduction to Metazoa Metazoa commonly known as Animalia and are multicellular organisms Protozoans were initially recognized as animals but once scientists concluded there polyphyletic ancestry making them no longer classified as a true kingdom Polyphyletic means there are multiple lineages and there is not one common ancestor The sister group to Metazoa are choanoflagellates Metazoan Tissues Metazoan cells are commonly organized by their tissue layers They have two main tissue layers epithelial and connective Epithelial tissues are tissues a layer of connecting cells covering the body or inner lining of a cavity The epithelial cells secrete a basal lamina which is connected by intercellular junctions Connective tissue is a tissue with widely spreaded cells that don t actually connect These cells are in the extracellular matrix ECM The Phylum Porifera Sponges and Placozoa don t contain epithelial tissue The Metazoan tissue is made of many 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 has microvilli 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 to support the cell and help it maintain its shape and structure The ECM is very important when it comes to cell and tissue development and physiology Collagen is a fibrous protein that s unique to metazoans They form a triple helix with polysaccharide forming an important component of skin and bone Intercellular Junctions Intercellular Junction is a part of the epithelial tissue They are commonly defined by either being gap or belt junctions Gap junctions are directly connected to the cytoplasm and adjacent cells The cell membrane around one cell has a small amount of space between it and the adjacent cell Gap junction s main function is to ensure that adjacent cells are able to communicate with one another This space is so small is can be measured in nanometers These small spaces only allow small particles to go through them so proteins are unable to travel between these gap junctions Another type of junction is belt junctions unlike gap junctions which are located on the lower region of a cell belt junctions are near the top part of the cell Belt junctions are tight junctions and act as a barrier for diffusion for proteins and lipids They also act as a seal between adjacent cells Another intercellular junction is hemidesmosome Hemidesmosome has a function to connect a cell to the ECM using adhesion proteins Desmosome are dense plaques of protein acting as anchors for intermediate cell cytoplasm filaments Origin of Metazoa Metazoans where introduced earlier in the notes but their origin can be traced back to two theories the colonial and syncytial theory The original theory states that Metazoa derived from flagellated Protzoa that were in colonies The original theory is supported by molecular and morphological data which is introduced in lecture one notes The syncytial theory believes that Metazoa derived from a multinucleate and unicellular organism called a syncytium Syncytium is a large cell with multiple nuclei Embryology Embryology is the study of the way cells develop and reproduce There s terminology the student must first understand before studying embryology such as cleavage gastrulation and germ layers Cleavage is the process where cells begin to separate and form new cells during reproduction Gastrulation is the process where germ layers begin to develop Germ layer is the three layers that line within the organism Metazoans undergo various steps during reproduction The first step is when two haploid cells combine to make a zygote next is cleavage where the cell divides without growth This step makes the zygote develop into the blastula The blastula is simply what the embryo is called when it s in the early stages of development Then the process of gastrulation begins and this is where the germ layers begin forming The germ layers are the endoderm mesoderm and ectoderm The endoderm lines the inner part of the organism the mesoderm separates the endoderm and ectoderm The ectoderm is known as the outer germ layer Important Terminology Eggs Animal Pole Zygote surface that the nucleus is closest to Vegetal Pole Opposite side to the animal pole Cleavage Holoblastic Whenever the entire zygote divides Meroblastic When only certain regions of the zygotes surface divides Blastomers The surfaces that are divided during cleavage o Micromeres Smaller sizes of the zygote that result from unequal cleavage o