Lecture 2 Animal Development_student

Core Concepts of Biology

5 Core Concepts of Biology Related to Animal Development:

1. Structure & Function: This concept delves into the interconnection between the physical architecture of biological structures and their operational roles. For example, the unique design of cartilage offers flexible strength, which is vital for organisms to maintain mobility while providing necessary support and protection for various bodily functions. This illustrates how the inherent physical properties of biological entities influence their functional capacities and interactions with other systems.

2. Evolution: A profound understanding of evolutionary biology helps elucidate how developmental processes have adapted over time, leading to a diversity of traits seen among different species. This encompasses the gradual change in genetic characteristics across generations, illustrating how natural selection shapes developmental mechanisms and, ultimately, the survival of organisms in varied environments.

3. Systems: Biological systems consist of interconnected entities that function in coordination to sustain life. Cells, as the fundamental units of life, engage in intricate relationships that work in unison to maintain homeostasis. Feedback mechanisms are critical in facilitating communication within these systems, thus ensuring stability and balance throughout the organism, underscoring the complexity of biological processes.

4. Information Flow: This principle pertains to how genetic information is conveyed and expressed, which plays a vital role in controlling development and function throughout an organism’s life stages. The flow of information from DNA to RNA to protein synthesis regulates diverse cellular activities and interactions, guiding development from the embryonic stage through maturity.

5. Transformations of Energy and Matter: This concept emphasizes the essential role that energy derived from food plays in biological processes. Organisms convert energy from their food sources into chemical energy necessary for various physiological activities, including growth and maintenance of cellular structures. This highlights the interrelationship between energy usage and matter in sustaining life processes.

Understanding and Example:

• An effective illustration of the Structure & Function principle can be seen in the specialized design of cartilage, which enables flexibility and strength. This structural capability allows for effective movement and support within the body, while also providing protection to joints and other sensitive regions.

Key Biological Systems:

• Cells act as integral components of complex biological systems, interacting to maintain homeostasis through sophisticated feedback loops. Understanding these interactions sheds light on the myriad biological processes essential for life, exemplifying the intricate webs of relationships among various cellular and systemic components.

Physiological Functions:

• The diverse physiological activities of organisms necessitate energy, which is procured from food resources. This energy not only fuels fundamental metabolic functions but also supplies vital building blocks required for the ongoing development and maintenance of tissues, organs, and systems within the organism.

Today's Lecture Topics

• L02: Animal Development

• In-depth examination of Model Organisms: This lecture focuses on the use of model organisms, specifically Sea Urchins and Frogs, that are extensively utilized in developmental biology research due to their experimental accessibility and relevance in studying conserved developmental processes across species.

• Key Stages of Development:

  • Fertilization: The crucial initial process in which haploid gametes from male and female organisms unite to form a diploid zygote, marking the beginning of developmental processes. 2 Haploid gametes (egg. sperm), one cell divides to make multicellular diploid. Haploid gametes join to form a diplod zygote.

  • Video

  • Egg cytoplasm contains many proteins and mRNA involved in early development.

  • moms side

  • Zygote: The single-cell stage resulting from fertilization, which serves as the foundation for all subsequent stages of development.

  • Cleavage: A phase characterized by rapid sequences of cell division without growth, transforming the zygote into a multicellular entity through successive rounds of division into smaller cells.

  • Blastula: The developmental stage where the embryonic structure forms a hollow ball of cells, filled with a central fluid cavity called the blastocoel, establishing the groundwork for further differentiation.

  • Differential Gene Expression: The process by which cells express unique genes based upon their spatial and temporal locations, resulting in diverse cellular structures and functions essential for the organism's development.

  • Cytoplasmic Determinants: Intracellular molecules that influence developmental fates based on their localization within the cell, contributing to asymmetries that dictate cell differentiation.

  • Inductive Signals: Signaling cues that originate from neighboring cells or the external environment, steering developmental outcomes by eliciting specific cellular responses.

  • Morphogenesis: The biological process responsible for the organized shaping of the organism, involving cellular movements, growth, and differentiation to establish body plans and structures.

  • Gastrulation: A pivotal phase during which the blastula undergoes extensive reorganization, forming three primary germ layers: ectoderm, mesoderm, and endoderm, which will later differentiate into various organ systems.

  • Organogenesis: The subsequent formation and development of organs that arise from the established germ layers, culminating in the creation of functional anatomical systems.

  • Programmed Cell Death: Also known as apoptosis, this regulated process is vital for eliminating redundant or damaged cells, contributing to the precise shaping of the organism during development.

Break Time: A brief intermission of 5-10 minutes is incorporated into the lecture schedule, providing students the opportunity to refresh and regroup before continuing with the stated topics.

Overview of Fertilization and Development

Key Concepts Discussed:

• A thorough understanding of the entire process from a single unicellular zygote to the emergence of complex multicellular structures is fundamental to developmental biology. This progression includes how individual cells differentiate and specialize to form a multitude of tissues and organs that are essential for the functionality and survivability of the organism.

Stages of Development:

1. Fertilization: This stage involves the pivotal event where the haploid gametes from male and female organisms successfully merge, forming a diploid zygote. This initial fusion marks a critical milestone, initiating a cascade of developmental processes.

2. Cleavage: Following fertilization, cleavage involves a series of rapid cell divisions that occur without an increase in overall cellular mass. This results in the segmentation of the zygote into smaller units called blastomeres, ultimately transforming it into a multicellular structure.

3. Blastula Formation: As cleavage continues, the structure develops into a blastula, characterized as a hollow sphere of cells surrounding a fluid-filled cavity, known as the blastocoel. This formation is essential as it sets the stage for subsequent differentiation and organization during development.

4. Differential Gene Expression: Throughout development, diverse sets of genes are activated at different times and locations within the embryo. This variability in gene expression regulates the functions and identities of cells, ultimately leading to the formation of specialized tissues and organs.

5. Morphogenesis: This complex process entails the orchestrated movements of cells and tissue organization that lead to the development of the organism's body plan and physical features. Morphogenesis establishes the architecture necessary for functional organ systems and overall organismal shape.

Cleavelage is the process by which the zygote becomes multicellular.

• Cleavage involves a series of rapid cell divisions that transform the single-celled zygote into a multicellular structure known as the blastula, setting the stage for subsequent developmental processes.

• Rapid cell division with little growth of individual cells (G1 and G2 phases skipped). As cleavage progresses, the blastula undergoes further differentiation and organization, leading to the formation of distinct germ layers that will give rise to various tissues and organs in the developing embryo.

Cleavage results in many smaller cells called blastomeres.

• Cells getting smaller and smaller with each round of division. This process is crucial as it establishes the foundational architecture of the embryo, enabling the eventual specialization of cells into specific functions.

• No growth of cells between divisions. Instead, the overall size of the embryo remains constant while the number of cells increases, allowing for more complex structures to emerge as development continues.

The blastula is a hollow ball of cells with a fluid filled cavity called the blastocoel.

• Animal pole

• Blastocoel

Vegetal pole: The region of the blastula opposite the animal pole, typically containing a higher concentration of yolk

How can cells that possess the same genome look and behave differenttly?

Differential gene expression

How does a cell know what genes to express at any given time? Two mechanisms:

• Cytoplasmic determinants: the signal comes from within the cell.

• Inductive signal: the signal comes from outside the cell. These mechanisms play crucial roles in determining cell fate during development, ensuring that cells respond appropriately to their internal and external environments.

Respuestas a las preguntas: 1.- B 2.- T 3.- T 4.- B

Morphogenesis is the rearrangement of cells or sheets of cell in the embryo

• Gastrulation: Stage when the three germs layers are established, and the basic body plan is set up. Three layered gastrula: ectoderm, mesoderm, endoderm

• Organogenesis; Is the formation of the organs.

  Frog Gastrulation.

1. Cell in the vegetal hemisphere push inward. Cell moves to the inside. During this process, the cells undergo extensive rearrangement, leading to the formation of the archenteron and ultimately contributing to the development of the gut.

2. Outer cells (future endoderm and mesoderm) roll inward. This process is crucial as it establishes the basic body plan and layers of the embryo, leading to the development of various organ systems.

3. Blastocoal collapses and new cavity - archenteron is formed, which will eventually develop into the digestive tract of the embryo.

4. Cell at the animal pole (future ectoderm) spread over the outer surface. This spreading of ectodermal cells is essential for the formation of the epidermis and nervous system, as these layers will give rise to critical structures such as skin and neural tissues.

5. At the end we end with 3 layersof cells known as the germ layers: ectoderm, mesoderm, and endoderm, each of which will differentiate into specific tissues and organs essential for the organism's development.

Respuesta a la pregunta: T

Morphogenesis is achieved through changes inn cell position, shape, and survival.

• Convergent extension is a key process during morphogenesis that involves the narrowing and lengthening of tissue, allowing cells to move closer together while extending the overall structure.

• Ectodermal cells change shape during neural tube formation, which is critical for the proper development of the central nervous system. This process is influenced by various signaling pathways that guide the cells in their transition from a flat epithelial sheet to a three-dimensional structure.

• They elongate microtubules , which play a crucial role in maintaining the shape and integrity of the developing neural tube, facilitating the process of convergent extension.

• actin filaments also play a significant role in this transformation by providing the necessary contractile force that facilitates cell shape changes and movements during the process.

• will split and form another neural tube

Programmed cell death also shape embryos. Pregunta: ALL OF THE ABOVE