Animal Form and Function BIOL 1306 PDF

Animal Form and Function BIOL 1306: Biology 1 for Majors Jenifer Gifford, Ph.D. [email protected] 1. Explain the concepts of adaptations and fitness tradeoffs 2. Explain the difference between Adaptation and Acclimatization 3. Describe the four types of tissues 4. Describe the three types of skeletal...

Animal Form and Function BIOL 1306: Biology 1 for Majors Jenifer Gifford, Ph.D. [email protected] 1. Explain the concepts of adaptations and fitness tradeoffs 2. Explain the difference between Adaptation and Acclimatization 3. Describe the four types of tissues 4. Describe the three types of skeletal systems 5. Explain how muscles and skeletal systems function together to facilitate movement. 6. Describe the three components of a homeostatic system and explain the importance of homeostasis 7. Explain why homeostasis is important for organismal systems Anatomy and Physiology Animals are generally studied through their anatomy and physiology: Anatomy refers to an organism’s physical structure or form • Ex. An elephant’s large ears are loaded with blood vessels Physiology is the study of how the physical structures in an organism function • Elephants shunt blood to the surface of their ears where body heat can be transferred to the environment Biologists who study animal anatomy and physiology are studying adaptations: • Adaptations are heritable traits that make individuals more likely to survive and reproduce in a certain environment better than individuals that lack those traits. • In other words, adaptations increase fitness 1 Adaptations are traits coded for by Genes • Physical traits such as large ears develop due to genes inherited from parents. • Elephants with alleles for larger ears have a better chance to survive in their environment and produce more viable offspring than elephants with alleles for smaller ears. • When elephants reproduce, they pass those alleles onto their offspring, who are also able to survive and reproduce. • Favorable alleles tend to become more prevalent in a population from generation to generation. Genes code for proteins that determine traits Gene associated with hereditary Hemochromatosis (HFE) is located on chromosome 19 HFE Gene: Normal Allele HFE Gene: Hemochromatosis Allele Favorable traits accumulate in populations over time Alleles are different sequences of the same gene. New/different sequences lead to new/different traits Survival of the Fit Enough Pumpkin Toadlet • If a mutation results in a structure that is significantly inefficient, those organisms tend to not survive or produce viable offspring and the mutated allele does not persist or become prevalent in the population. Fitness Tradeoffs Important constraint on adaptation may be trade-offs: Energy is needed to produce offspring just as energy needed to mount immune response during an infection. Animals may not have enough to satisfy both needs Hypothesis: Crickets make an energy tradeoff between reproduction and immune responses • Evolution does not move toward perfection. Individuals just need to be good enough to survive and mate to pass on their genes. • This is why some unfavorable traits and inefficient structures or behaviors exist in populations 2 Fitness Tradeoffs Fitness Tradeoffs Hypothesis: Crickets make an energy tradeoff between reproduction and immune responses Hypothesis: Crickets make an energy tradeoff between reproduction and immune responses Conclusion: While excessively producing spermatophores, crickets have a lowered immune activity Conclusion: While responding to an infection, crickets produce smaller spermatophores Adaptation vs. Acclimatization • Adaptations are due to permanent, genetic changes in a population, in response to pressure exerted by environment (natural selection) • Ex. Baseline skin color or high altitude tolerance in Tibetan population. • Acclimatization/acclimation is a phenotypic change that occurs in an individual in response to environmental fluctuations • Short term and reversible • Possible due to genes that already exist. • Ex. Altitude acclimatization or getting a tan 3 Recall: Structure Determines Function Recall: Cells With Common Function Form Tissues Correlations between structure and function begin at molecular level: • Protein shape correlates with their roles as enzymes, structural components of cell, or transporters. Similar correlations between structure and function occur at the cellular level: • Example: Secretory cells that secrete digestive enzymes have a larger plasma membrane surface area to accommodate more pumps and channels and more rough ER and Golgi compared to non-secretory cells Animals are multicellular and their bodies contain distinct types of cells that are specialized for different functions. • Tissue: Group of similar cells that work together as a unit to perform the same function. Most adult animals have four tissue types: Epithelial, Connective, Muscle, and Nervous Epithelial Tissue Epithelial tissues (epithelia) are tissues that cover the outside of the body, line surfaces of organs, and form glands (group of cells that secrete specific molecules or solutions) • Epithelia divided into two major types: • Simple epithelia: • Only a single cell layer thick • Allow gases, water, nutrients, and other substances to move across easily • Stratified epithelia: • Layers of closely packed cells • Protect body surfaces from environment Understanding Proper Tissue Architecture Helps with Diagnostics and Pathology Normal Lung Lung Tumor 4 Connective Tissue Connective tissue consists of cells loosely arranged in a liquid, jellylike, or solid matrix: Matrix is made of extracellular fibers (Collagen, reticular fibers, and elastin) and other materials. It is secreted by connective tissue cells themselves The nature of the matrix determines the overall nature of the connective tissue Four types of connective tissue: 1. Loose connective tissue— contains an array of fibrous proteins in a soft matrix: • Examples: Adipose and Fat Tissue 2. Dense connective tissue— contains a matrix dominated by tough collagen fibers that are secreted by fibroblasts: • Connective Tissue 3. Fluid connective tissue— cells surrounded by a liquid extracellular matrix: • Example: Blood, which contains a variety of cell types and has a specialized extracellular matrix 4. Supporting connective tissue—has a firm extracellular matrix: • Examples: Bone and Cartilage Examples: tendons, ligaments Significance of the Skeletal System Skeletal systems have four functions: 1. Protection from physical and biological assaults 2. Maintenance of body posture 3. 4. Re-extension of shortened muscles Transfer of muscle forces to other parts of the body and the environment Three types of skeletal systems: a) Hydrostatic skeletons use hydrostatic pressure of enclosed body fluids or soft tissues to support the body b) Exoskeletons have rigid structures on the outside of the body c) Endoskeletons have rigid structures inside the body 5 Diversity of Skeletal System Diversity of Skeletal System Soft-bodied animals have hydrostatic skeletons The exoskeleton is an exterior skeleton that encloses and protects an animal’s body Structure: An extensible body wall in tension surrounding a fluid or deformable tissue under compression • Insects have an exoskeleton that consists of cuticle made up of proteins and chitin: • This pressurized fluid enables softbodied animals to maintain posture, reextend muscles, and transfer muscle forces to the environment • The body wall of hydrostats may include different numbers and orientations of muscle layers and fiberreinforced cuticles or connective tissues • The interior may include seawater, coelomic fluid, blood, or soft organs • Crustaceans have a cuticle that is mineralized with calcium carbonate which makes their exoskeleton thick and hard • Paired flexor/extensor muscles operate jointed skeletons • Muscles must be packed INSIDE the skeleton • The exoskeleton must be shed (molted) in order for internal parts to grow • Hydrostatic skeletons composed of mostly muscle are called muscular hydrostats Diversity of Skeletal System Endoskeletons are rigid structures in the body; take a variety of structural forms: • Sponges secrete spicules that provide structural support • Echinoderms have endoskeletons that consist of calcium carbonate plates beneath the skin • Vertebrate endoskeleton is composed of rigid levers separated by joints— vertebrates change their shape largely by changing joint angles rather than body segments Vertebrate skeletons are variations on an ancient theme • The vertebrate skeletal system provided the structural support and means of location that enabled tetrapods to colonize land. • Evolved into amphibians, reptiles, birds and mammals Advantages: • Grows with the animal • Supports the weight of large animals • Protects vital internal organs • Protected by outer tissues • Allows flexible and more complex movements Functions • Support of the body • Protection of vital internal organs • Sites for muscle attachment • Storage reservoir for ions • Production of blood cells 6 Diversity of Skeletal System Vertebrate skeletons are composed of three main elements: Bone Anatomy Bones store calcium and other minerals Osteoblasts are bone-building cells that secrete protein and calcium-rich extracellular matrix 1. Bones—have cells in a hard extracellular matrix: • Bones interact at articulations or joints 2. Cartilage—has cells scattered in a gelatinous matrix of polysaccharides and protein fibers 3. Ligaments—bands of fibrous connective tissue that binds bones to other bones Bones attach to skeletal muscle via bands of fibrous connective tissue called tendons Healthy bones resist stress and heal from injuries Osteoclasts are boneresorbing cells that secrete acid onto bone tissue when blood calcium levels are low to cause small amounts of mineral to be resorbed into the blood Osteocytes – mature bone cells • Osteoblasts that become caught in the matrix • Live within the lacunae of osteons • Affect the timing and location of bone remodeling Joints permit different types of movement • Bones are living structures • Bones are connected at joints • Bone cells repair bones reshape bones throughout life • Joints allow limited movement of bones. • Broken bones are realigned and immobilized, and bone cells build new bone, healing the break Osteoporosis is a bone disease characterized by low bone mass and structural deterioration • Osteoclasts tend to be more active than osteoblasts • less likely if a person has high levels of calcium in the diet, sufficient intake of vitamin D, exercises regularly, and does not smoke • Bands of strong fibrous connective tissue called ligaments hold together the bones of movable joints. • Different joints permit various movements • Ball-and-socket joints enable rotation in the arms and legs. • Hinge joints in the elbows and knees permit movement in a single plane. • Pivot joints enable the rotation of the forearm at the elbow. Head of humerus Humerus Scapula Ulna Ball-and-socket joint Hinge joint Ulna Radius Pivot joint 7 Joints permit different types of movement Joints are supported by connective and muscle tissue Knee Joint/Hinge Joint: • Ligaments and tendons hold the bones/muscles in position to each other • Cartilage: Provides cushion and weight support Muscles/Bone Interaction • Muscles are attached to bone by tendons. • Vertebrate skeletons move by changes in joint angles controlled by antagonistic muscle groups: • Flexors pull bones closer together, decreasing joint angles between them • Extensors increase the angle of a joint, straightening it out Ligaments: Bone to Bone Tendons: Bone to Muscle Muscle Cell and Tissue Differences • Voluntary muscles contract in response to conscious thought; stimulated by neurons in the somatic division • Involuntary muscles contract in response to unconscious electrical activity; stimulated and inhibited by neurons in the autonomic division • Multinucleate vs uninucleate • Striated vs Unstriated Smooth and Cardiac Muscle • Unbranched, tapered at each end, and often organized in thin sheets • Lack the sarcomeres that are found in skeletal and cardiac muscle • Unstriated and appear smooth • Relatively small and have a single nucleus • Essential to function of lungs, blood vessels, digestive system, urinary bladder, and reproductive system • Makes up walls of the heart and responsible for pumping blood throughout the body: • Contain sarcomeres and are striated • Have a unique branched structure, directly connected end to end by intercalated discs: • These discs are critical to the flow of electrical signals from cell to cell and to coordination of the heartbeat 8 Skeletal Muscle • Consists of long, unbranched, multi-nucleate muscle fibers • Formed by fusion of many smaller embryonic cells during development • Each fiber is packed with myofibrils, each made of many sarcomeres that give it a striated appearance • Attached to bones; exerts a pulling force on bones when contracting, causing the skeleton to move • Encloses openings of the digestive system and urinary tracts; controls swallowing, defecation, and urination • During load-bearing exercise, muscle fibers synthesize additional contractile proteins and become larger: • No new cells are formed, but the increased size of the fibers allows the muscle to do more work Sarcomeres are the unit responsible for muscle contraction Skeletal Muscle • Voluntary; must be stimulated by somatic motor neurons: • Damage to these neurons will result in paralysis • The force output of skeletal muscle depends on: 1. The relative proportion of different fiber types 2. The organization of fibers within the muscle 3. How the muscle is used Sarcomeres are the unit responsible for muscle contraction • Vertebrate skeletal and cardiac muscle tissue is composed of long, slender cells called muscle fibers • Within each muscle fiber are many threadlike, contractile structures called myofibrils: • Myofibrils often look striated due to alternating light-dark units called sarcomeres • Sarcomeres shorten as myofibrils contract and lengthen when the cell relaxes and an external force stretches the muscle • The filaments slide past one another during a contraction • The sarcomere shortens with no change in lengths of the thin and thick filaments themselves 9 Sarcomeres are the unit responsible for muscle contraction • Myosin is the motor protein responsible for sliding the actin filaments during contraction. • Each myosin head can bind to actin—the head catalyzes the hydrolysis of ATP • Myosin and actin are locked together after an animal dies, stuck in rigor mortis: • Because ATP is unavailable, data suggested that ATP is required for myosin to release actin Muscle Composition Influences Behavior The breast muscle of birds is responsible for the contraction and relaxation of the muscles that flap wings. 1. Which birds (chickens vs. ducks) rely more heavily on the ability to fly long distances to survive/mate/find food? 2. Would long distance flying be associated more with endurance or short bursts of power? 3. What would you predict about the muscle fiber composition of each bird’s breast muscle based on their flying behaviors? Skeletal Muscle Fiber Types Slow twitch muscle fibers • Appear red due to high myoglobin concentration • Contract slowly because myosin hydrolyzes ATP at a slow rate • Fatigue slowly due to a high concentration of mitochondria that can generate a steady stream of ATP generated by aerobic respiration Fast twitch muscle fibers • Appear white due to low concentration of myoglobin • Contract rapidly because myosin hydrolyzes ATP at a rapid rate • Can fatigue easily because the primary source of ATP is glycolysis Intermediate muscle fibers • Appear pink or red • Contractile properties vary but are intermediate between slow and fast fibers • Obtain ATP from both glycolysis and aerobic respiration Nervous Tissue Nervous tissue consists of nerve cells (neurons) and several types of supporting cells 4. Think about the meat (muscle) we eat off of ducks and chickens. Where is the “white meat”? Where is the “dark meat”? 5. Does this make sense with what you discussed regarding the animal behavior for each bird in the previous questions? • Most neurons have two distinct types of projections: • Short, branching dendrites, which transmit electrical signals from adjacent cells to the neuronal cell body • Long axons, which carry electrical signals from the cell body to other cells 10 Nervous Tissue Nervous tissue transmits electrical signals (action potentials) by changing the permeability of the cell’s plasma membrane to ions, thus changing the charge across the membrane. Tissues Come Together To Form Organs An Organ is a structure that serves a specialized function and consists of several tissues Example: The small intestine is composed of muscle, nervous, connective, and epithelial tissue Organs systems consist of groups of tissues and organs that work together to perform one or more functions Tissues are organized into organs Organs are organized into Organ Systems Electrical signals in neurons convert to chemical signals (signaling molecules) at synapses and affect the behavior of muscle tissue. Important Concept To Recall: Folded Surfaces Maximize Surface Area and Environmental Interactions Recall the relationship between the surface area and volume of the roots and shoots in plants affects water and light absorption. In animals it is important because oxygen and nutrients must diffuse into an animals cells. Wastes must diffuse out. • Adaptations that increase surface area increase the efficiency of absorption and diffusion 11 Homeostasis is the regulation of internal conditions Homeostasis (“alike-standing”): Stability in chemical and physical conditions within an organism’s cells, tissues, and organs Internal conditions can remain relatively stable even though an organism’s environment may change • Most animals have regulatory systems that constantly monitor internal conditions: • Temperature, blood pressure, blood pH, salt/water balance, and blood glucose • Two different approaches to maintaining homeostasis—regulate or conform. (Most animals fall somewhere between these two extremes) • Homeostatic systems are regulated by negative feedback: • Effectors return internal conditions to set-point values • Examples: Cooling, heating, and behavioral and physiological responses to body temperature Internal Environments can protein/enzyme function: • Recall: Enzymes are proteins that catalyze chemical reactions within the cells • Temperature, pH, salt concentration and other physical and chemical conditions have dramatic effect on structure and function of proteins • Recall: disruption of protein structure disrupts function • Molecules, cells, tissues, organs, and organ systems function at an optimal level when homeostasis occurs General Homeostatic Mechanism Homeostatic system is based on three general components: 1. Sensor: Detects the Change 2. Integrator: Generates the Signal for Compensation 3. Effector: Behavioral/ Hormonal effects that diminish the change Why Homeostasis is Important Response: Heating stops. Room temperature decreases. Sensor/ control center: Thermostat turns heater off. Stimulus: Room temperature increases. Set point: Room temperature at 20 °C Stimulus: Room temperature decreases. Room temperature increases. Response: Heating starts. Epithelial Tissue is the Interface Between Internal and External Conditions • Epithelial tissues act as interface between internal and external environments and play key role in achieving homeostasis: • Epithelia are responsible for forming and maintaining an internal environment that is dramatically different from the external environment Sensor/ control center: Thermostat turns heater on. • Feedback systems usually work in “antagonistic pairs” • Input from sensors and integrators happen continuously 12 Specific mechanisms of homeostasis will be covered as we discuss organ systems 13