BIO 152 Study Guide week 9

Compare and contrast simple vs. complex multicellular organisms

- A key functional challenge of complex multicellularity is transporting food, oxygen, and molecular signals rapidly across large distances within the body-- by diffusion. - But oxygen absorbed by your lungs doesn't reach your toes by diffusion alone-it is transported actively, and in bulk, by blood pumped through your circulatory system - For complex multicellular organisms to function, bulk flow of oxygen, nutrients, and signaling molecules, at rates and across distances far larger than can be achieved by diffusion alone is needed. - simply multicellular organisms are able to use diffusion for the transportation of their nutrients - simple multicellular organisms due not experience cellular differentiation often nor do they communicate; they also all have direct communication with the external environment - no need for communication since all simple cells have direct communication with environments and transport their own nutrients (no need to communicate with other cells) - Complex multicellular organisms have differentiated cells and tissues. Moreover, in simple multicellular organisms, all or nearly all cells are in direct contact with the environment. In complex multicellular organisms, most cells are completely surrounded by other cells.

Explain the limitations to diffusion and the role of bulk flow in complex multicellular organisms

- Bulk flow is any means by which molecules move through organisms at rates beyond those possible by diffusion across a concentration gradient - diffusion alone cannot transport a complex multicellular organism's nutrients very far all alone - that oxygen binds to molecules of hemoglobin in red blood cells and then is carried through the bloodstream to distant sites of respiration. We circumvent/avoid diffusion by actively pumping oxygen-rich blood through our bodies. Most invertebrate animals lack well-defined blood vessels instead they have other mechanisms that circulate fluids freely throughout the body cavity. Indeed, without a mechanism like bulk flow, animals could not have achieved the range of size, shape, and function familiar to us. - Complex organisms other than animals also rely on bulk flow. A redwood tree must transport water upward from its roots to leaves that may be 100 m above the soil. If plants relied on diffusion to transport water, they would be only a few millimeters tall. How, then, do they move water? - Plants move water by bulk flow through a system of specialized tissues powered by the evaporation of water from leaf surfaces - Vascular plants also have specialized tissues for the transport of nutrients and signaling molecules upward and downward through roots, stems, and leaves. -Multicellular fungi transport nutrients through networks of filaments that may be meters long, relying on osmosis to pump materials from sites of absorption to sites of metabolism. - in general, when some cells within an organism are buried within tissues, far from the external environment, bulk flow is required to supply those cells with molecules needed for metabolism. **One of the key limitations as organisms increase in size (and in cell number) is diffusion. While diffusion is effective over short distances, such as within and between close cells, it is far too slow over longer distances to allow the maintenance of cell functions in a larger organism. So, as some groups of organisms evolved larger sizes, they also evolved mechanisms to allow the movement of needed molecules in bulk, like circulatory systems in animals and xylem and phloem in plants.**

Explain the processes of animal reproduction and embryonic development

- Most animals are diploid organisms, meaning that their body (somatic) cells are diploid and haploid reproductive (gamete) cells are produced through meiosis - The majority of animals reproduce sexually, distinguishing animals from fungi, protists, and bacteria, where asexual reproduction is common or exclusive. - During sexual reproduction, the haploid gametes of the male and female individuals of a species are formed by meiosis and then combine in a process called fertilization - fertilization produces a diploid egg called a zygote. -- Typically, the small, motile male sperm fertilizes the much larger, sessile female egg - After fertilization, a series of developmental stages occur during which primary germ layers are established and reorganize to form an embryo. 1. The process of animal development begins with the cleavage, or series of mitotic cell divisions, of the zygote. 2. Three cell divisions transform the single-celled zygote into an eight-celled structure 3. After further cell division and rearrangement of existing cells, a 6-32-celled hollow structure called a blastula is formed 4. Next, the blastula undergoes further cell division and cellular rearrangement during a process called gastrulation. 5. This leads to the formation of the next developmental stage, the gastrula, in which the future digestive cavity is formed 6. Different cell layers (called germ layers) are formed during gastrulation. 7. These germ layers are programmed to develop into certain tissue types, organs, and organ systems during a process called organogenesis.

Describe the features that distinguish the kingdom Animalia from other kingdoms

- One the key reasons is that unlike plants and fungi, animal cells do not have a cell wall. - While cell walls are an asset in an aqueous environment where they play a role in maintaining water balance (keep the cell from exploding in hypotonic conditions), cell walls can also be a restriction in terms of movement and growth - all animals are eukaryotic, multicellular organisms, and almost all animals have a complex tissue structure with differentiated and specialized tissues - most animals are motile, at least during certain life stages. - All animals are also heterotrophic, ingesting other living or dead organisms; this feature distinguishes them from autotrophic organisms, such as most plants, which synthesize their own nutrients through photosynthesis - As heterotrophs, animals may be carnivores, herbivores, omnivores, or parasites - Most animals also reproduce sexually, and the offspring pass through a series of developmental stages that establish a determined and fixed body plan, morphology of an animal, determined by developmental cues. - While animal cells do not have a cell wall, the cells may be embedded in an extracellular matrix (such as bone, skin, or connective tissue), and animal cells have unique structures for intercellular communication (such as gap junctions). TISSUES: - animals possess unique tissues, which allow coordination (nerve tissue) of motility (muscle tissue). - Animals are also characterized by specialized connective tissues that provide structural support for cells and organs - This connective tissue constitutes the extracellular surroundings of cells and is made up of organic and inorganic materials. -connective bone tissue supports the entire body structure and the activities of vertebrates - Epithelial tissues cover, line, protect, and secrete. Epithelial tissues include the epidermis of the integument (hair, scales, feathers, hooves, and nails), and the lining of the digestive tract and trachea. - Epithelial tissues also make up the ducts of the liver and glands of advanced animals. - The different types of tissues in true animals are responsible for carrying out specific functions for the organism. This differentiation and specialization of tissues is part of what allows for such incredible animal diversity. - the evolution of nerve tissues and muscle tissues has resulted in animals' unique ability to rapidly sense and respond to changes in their environment. This allows animals to survive in environments where they must compete with other species to meet their nutritional demands.

Describe the different parts of the neuron and their functions

- The visual system is processing what is seen on the page; the motor system controls the turn of the pages (or click of the mouse); the prefrontal cortex maintains attention. - A nervous system is an organism's control center: it processes sensory information from outside (and inside) the body and controls all behaviors. - Regardless of the animal, the nervous system is made up of neurons, specialized cells that can receive and transmit chemical or electrical signals, and glia, cells that provide support functions for the neurons by playing an information processing role that is complementary to neurons. - different types of neurons have different sizes and shapes that relate to their functional roles. PARTS: - Like other cells, each neuron has a cell body (or soma) that contains a nucleus, smooth and rough endoplasmic reticulum, Golgi apparatus, mitochondria, and other cellular components. - Neurons also contain unique structures, for receiving and sending the electrical signals that make neuronal communication possible. - Most neurons contain dendrites, which receive these signals, and axons that send signals to other neurons or tissues. - **Dendrites** are tree-like structures that extend away from the cell body to receive messages from other neurons at specialized junctions called **synapses** - Dendrites can also have small protrusions called dendritic spines, which further increase surface area for possible synaptic connections. - Once a signal is received by the dendrite, it then travels passively to the cell body. The cell body contains a specialized structure, the **axon hillock** that integrates signals from multiple synapses and serves as a junction between the cell body and an axon - An **axon** is a tube-like structure that propagates the integrated signal to specialized endings called **axon terminals** - Chemicals released at axon terminals allow signals to be communicated to these other cells. - Neurons usually have one or two axons, but some neurons, like amacrine cells in the retina, do not contain any axons - some axons are covered with **myelin**, which acts as an insulator to minimize dissipation of the electrical signal as it travels down the axon, greatly increasing the speed on conduction. - This insulation is important as the axon from a human motor neuron can be as long as a meter—from the base of the spine to the toes. - Myelin is produced by glial cells. Along the axon there are periodic gaps in the **myelin sheath**. These gaps are sites where the signal is "recharged" as it travels along the axon. - It is important to note that a single neuron does not act alone—neuronal communication depends on the connections that neurons make with one another (as well as with other cells, like muscle cells). Dendrites from a single neuron may receive synaptic contact from many other neurons.

Differentiate between different types of neurons

- There are four different types of neurons, and the functional role of a given neuron is intimately dependent on its structure - neurons can be broadly divided into three basic types: unipolar, bipolar, multipolar. - **Unipolar cells** have one long axon emerging from the cell body, but the cell body is located at neither end of that axon - At one end of the axon are dendrites, and at the other end, the axon forms synaptic connections with a target cell. - Unipolar cells are exclusively sensory neurons and have their dendrites in the periphery where they detect stimuli. - These neurons are not found in vertebrates but are found in insects where they stimulate muscles or glands - **Bipolar cells** have two processes, which extend from each end of the cell body, opposite to each other - One is the axon and one the dendrite. Bipolar cells are not very common. They are found mainly in the olfactory epithelium (where smell stimuli are sensed), and as part of the retina in the eye. - A retinal bipolar cell, which receives signals from photoreceptor cells that are sensitive to light and transmits these signals to ganglion cells that carry the signal to the brain. - **Multipolar neurons** have multiple processes emerging from their cell bodies (hence their name, multipolar). - They have dendrites attached to their cell bodies and often, one long axon - Motor neurons are multipolar neurons, as are most of the CNS. Multipolar neurons are the most common type of neuron. - **pseudounipolar neurons** are sensory neurons that have no dendrites, the branched axon serving both functions. The peripheral branch extends from the cell body to organs in the periphery including skin, joints and muscles, and the central branch extends from the cell body to the spinal cord -Unipolar neurons have one axon. Bipolar neurons have an axon and one dendrite extending from the cell body toward opposite poles. Multipolar neurons have multiple dendrites and a single axon. - A bipolar neuron has a single dendrite that extends from the cell body, opposite the side from which the single axon extends. A pseudounipolar neuron has a single axon that splits into one brain that runs to the peripheral tissues and a second branch that leads to the spinal cord.

Describe the roles that Hox genes play in animal development and evolution

- These genes that determine animal structure are called "homeotic genes," and they contain DNA sequences called homeoboxes. - The animal genes containing homeobox sequences are specifically referred to as Hox genes. - This family of genes is responsible for determining the general body plan, such as the number of body segments of an animal, the number and placement of appendages, and animal head-tail directionality. - The first Hox genes to be sequenced were those from the fruit fly (Drosophila melanogaster). - A single Hox mutation in the fruit fly can result in an extra pair of wings or even appendages growing from the "wrong" body part. - what makes Hox genes so powerful is that they serve as master control genes that can turn on or off large numbers of other genes - Hox genes do this by coding transcription factors that control the expression of numerous other genes. - Hox genes are homologous in the animal kingdom, that is, the genetic sequences of Hox genes and their positions on chromosomes are remarkably similar across most animals because of their presence in a common ancestor, from worms to flies, mice, and humans - Hox genes have undergone at least two duplication events during animal evolution, with the additional genes allowing for more complex body types to evolve.

Describe the shared features of complex multicellular organism

- costs associated with multicellularity, particularly for complex multicellular organisms with differentiated reproductive tissues - most cells do not reproduce, instead supporting the few that do. This requires cooperation among cells, but it creates opportunities for cells to "cheat"-to use nutrients for their own proliferation rather than the growth and reproduction of the organism as a whole. (1) They have highly developed molecular mechanisms for adhesion between cells. (2) They display specialized structures that allow cells to communicate with one another. (3) They display complex patterns of cellular and tissue differentiation, guided by networks of regulatory genes (4) They have a three dimensional organization, so only some cells are in direct contact with the environment -Cells that are buried within tissues, relatively far from the exterior of the organism, do not have direct access to nutrients or oxygen -interior cells cannot grow as fast as surface cells unless there is a way to transfer resources from one part of the body to another -interior cells do not receive signals directly from the environment, even though all cells must be able to respond to environmental signals if the organism is to grow, reproduce, and survive. -Complex multicellular organisms, therefore, require mechanisms for transferring environmental signals received by cells at the body's surface to interior cells, where genes will be activated or repressed in response. **growth and development in complex multicellular organisms can be defined as increasing or decreasing gene expression in response to molecular signals from surrounding cells.** EXAMPLES -In plants, only some tissues photosynthesize or absorb organic molecules; other tissues transport food and oxygen through the body; and still others generate the molecular signals that govern development. - In both plants and animals, only a small subset of all cells contributes to reproduction. Because of this functional differentiation, cell or tissue loss can be lethal for the entire organism.

Describe the role of glial cells in neuron functioning

- the number of glial cells in the brain actually outnumbers the number of neurons by a factor of ten. - Neurons would be unable to function without the vital roles that are fulfilled by these glial cells. - Glia guide developing neurons to their destinations, buffer ions and chemicals that would otherwise harm neurons, and provide myelin sheaths around axons. - regulate homeostasis, providing support and protection to the function of neurons.

In what order are the following thought to have evolved to have given rise to complex multicellularity?

1. the ability of cells to divide 2. the ability of cells to stick together 3. ability of cells in a group to communicate via signalling 4. formation of structures to facilitate cell signalling

Place the following stages of embryonic development in order from the first event/structure that occurs after fertilization of the egg.

1. zygote 2. cleavage (mitotic division) without cellular rearrangement 3. 8-cell stage 4. cleavage and 1st set of cellular arrangements 5. blastula 6. cleavage and 2nd series cellular arrangements 7. gastrula

Which statements best describe a reasonable mechanism for animal structures evolving to become better suited for specific functions?

Animals with mutations that give rise to more effective structures will become more abundant Animals with mutations that allow them to be better at accessing resources are more likely to reproduce.

Which of the following is NOT a characteristic of an animal?

Cell walls composed of chitin. -- FUNGI

_________ indicate that the ion channels and ________ found in neurons are the result of __________ of an existing structure that was found in ___________

DNA sequences; voltage gated channels; an exaptation; bacteria

Compare the different functions of glial cells

Each type of glial cell has different functions and thus different interactions with the nervous system: - **Astrocytes** make contact with both capillaries and neurons in the CNS. They provide nutrients and other substances to neurons, regulate the concentrations of ions and chemicals in the extracellular fluid, and provide structural support for synapses, repairing damage, regulate communication - Astrocytes also form the blood-brain barrier—a structure that blocks entrance of toxic substances into the brain. Astrocytes become active in response to nerve activity, transmit calcium waves between neurons, and modulate the activity of surrounding synapses. - **Satellite glia** provide nutrients and structural support for neurons in the peripheral nervous system (PNS). - **Microglia** scavenge and degrade dead cells and protect the brain from invading microorganisms. - removed damaged neurons - the rest of the cells are macroglia - primary immune defense (travel throughout brain and spinal cord) - **Oligodendrocytes** form myelin sheaths around axons in the central nervous system (CNS). One axon can be myelinated by several oligodendrocytes, and one oligodendrocyte can provide myelin for multiple neurons. - **Schwann cells** form myelin sheaths around axons in the PNS where a single Schwann cell provides myelin for only one axon as the entire Schwann cell surrounds the axon. - **Radial glia** a give rise to new neurons (neurogenesis) and serve as scaffolds for developing neurons as they migrate to their end destinations. - **Ependymal cells** line fluid-filled ventricles of the brain and the central canal of the spinal cord. They are involved in the production of cerebrospinal fluid, which serves as a cushion for the brain, moves the fluid between the spinal cord and the brain, and is a component for the choroid plexus. - removing waste products from brain and protection

Which of the following life cycles is typical for animals?

I ** look at picture in quiz

Eukaryotic sexual life cycles show tremendous variation. Of the following elements, which do ALL sexual life cycles have in common?

II. Meiosis III. Fertilization IV. Gametes

Mitosis is commonly found in all but one of the following. Which is the exception?

a haploid animal cell

Myelin is an important component of nerve systems. What does it do?`

acts as an insulator to minimize electrical signal loss prevents the electrical signal from being "recharged" as it travels increases the speed of conduction of electrical signals

In which of these groups of organisms would you find mitochondria?

all eukaryotic organisms have mitochondria Algae Slime molds Plants Animals Fungi

Which of the following is NOT a feature common to most animals?

asexual reproduction

In order for complex multicellular organisms to function, the individual cells need to?

be able to move molecules by bulk flow be able to communicate with each other be attached to each other

Glial cells are very diverse, what are some of their functions in nervous systems?

buffer ions and chemicals around neurons provide myelin sheathing around axons modulate communication between nerve cells guide developing neurons to their destinations

What characteristics of multicellular organisms are found in sponges?

cell adhesion cell communication cell differentiation

Which of the following phenotypes would most likely be the result of a Hox gene mutation?

change in the number of limbs

Which of these processes in sponges is the result of diffusion?

circulation gas exchange excretion

In jellyfish (Cnidarians) the epidermis arises from the ________ and the gastrodermis arises from the __________ after gastrulation. In addition, jellyfish have a nerve net which arises from ______

ectoderm; endoderm; ectoderm

Sponge cells capture nutrients in the form of ____________ by the process of ____________.

food particles, endocytosis

During which stage of animal embryo development do the germ layers form?

gastrulation

After being formed by the ribosomes located on the endoplasmic reticulum, what is the next organelle to which a protein could be transported?

golgi apparatus The endomembrane system starts with the nucleus which is attached to the endoplasmic reticulum from which vesicles emerge that then go on to fuse to golgi apparatus from which vesicles emerge and fuse with either the plasma membrane or an internal membrane bound organelle (like the lysosomes or peroxisomes).

What tissues does the endodermal layer of tissue give rise to?

inner lining of the gut respiratory tract

What are some advantages of being multicellular?

it can provide protection against predation It can improve movement/locomotion through coordination

In animals, somatic cells are produced by ________ and gametic cells are produced by __________

mitosis; meiosis

_______ transmit information from one place to another using electrical impulses that travel through ______ in a specific pattern of connections that make up a _______

neurons; synapses, circuit

Animals are an incredibly diverse group. What features are often used to when scientists are classifying different animals?

number of tissue layers formed during development the presence or absence of a body cavity body plans and symmetry

What do all complex multicellular organisms have in common?

regulatory gene networks that control cell and tissue differentiation patterns highly developed cell-cell communication a means by which to hold cells together

Match the challenge to complex multicellularity with the adaptations that address them

the presence of cells with different phenotypes in the same organism: regulatory domains in the promotors of genes the ability of cells to stick together: integrins and cadherins the ability of cells to communicate with each other: hormones and receptors the ability to move molecules over long distances: xylem and phloem

Which of the following most accurately describe sponges?

they are sedentary filter feeders - Sponges do not move unlike other animals and they lack true tissues. They are simple multicellular animals.

How are proto-neurons thought to have evolved in early multicellular animals?

through natural selection for increased speed of transmitting information through mutation of bacteria ion channels through duplication of bacterial ion channel genes

Both Parazoa (sponges) and Eumetazoa ("true" animals) evolved from a common ancestral organism that resembles the modern-day protists called choanoflagellates.

true

The functional role of a given neuron is intimately dependent on its structure.

true

There are some cells in sponges that can change function during the sponges life.

true

gastrulation

which tissue layer gives rise to the different types of tissues seen later on in development. **Gastrulation: the dramatic rearrangement (movement) of cells in the blastula to create the embryonic tissue layers. These tissue layers will go on to produce the tissues and organs of the adult animal.** - zygote undergoes a series of cell divisions that result in blastula - blastomeres can be essential in trigger gastrulation - in gastrulation the blastula rearranges with sheets of blastomeres entering interior - by the end of gastrulation, three embryonic germ layers emerge —endoderm, mesoderm, and ectoderm—take their positions in the embryo. - —endoderm, mesoderm, and ectoderm—take their positions in the embryo. **The three germs layers, shown below, are the endoderm, the ectoderm, and the mesoderm. The ectoderm gives rise to the nervous system and the epidermis. The mesoderm gives rise to the muscle cells and connective tissue in the body. The endoderm gives rise to columnar cells found in the digestive system and many internal organs.** 1. At the beginning of gastrulation, a few surface cells, called bottle cells, move into the interior of the embryo, followed by other surface cel 2. The movement of cells into the embryo creates a lip, called the dorsal lip, over which sheets of cells continue to move inside. At the same time, the ectoderm extends around the embryo's surface in a process called epiboly. As gastrulation proceeds, a cavity, called the archenteron, forms while the blastocoel shrinks. 3. The archenteron is the primitive gut and is completely surrounded by endodermal tissue. The endoderm at the roof of the cavity originated from the outside of the embryo. The cavity is continuous with the outside, via the blastopore, which eventually becomes the anus of the animal. 4. As the ectoderm extends around the embryo, another set of bottle cells forms. These cells migrate into the embryo, and other surface cells follow them, creating the ventral lip of the blastopore. 5. By the end of gastrulation, the ectoderm has surrounded the embryo, endoderm lines the inside, and mesoderm lies between the two. Additionally, the fates of specific regions have become determined. 6. The endoderm gives rise to the digestive and respiratory tracts and associated structures. The mesoderm gives rise to the skeleton, circulatory system, muscles, excretory system, and most of the reproductive system. The ectoderm gives rise to the skin, sense organs, and nervous system. - In gastrulation, the three embryonic tissue layers move into the positions where they begin to develop into the adult's organs and tissues. **Ectoderm Brain and nervous system; lens of the eye; inner ear; lining of mouth and nasal canal; epidermis of skin; hair and nails; sweat glands; oil glands; milk secretory glands** **Mesoderm Skeletal system (bones, cartilage, notochord); gonads; muscle; outer coverings of internal organs; dermis of skin; circulatory system (heart, blood vessels, blood cells); kidneys** **Endoderm Inner linings of gut; respiratory tract (including lungs); liver; pancreas; thyroid; urinary bladder**