Animal Traits and Classification (Exam 3)

Animal Traits

• Animals are heterotrophic, ingesting food for nutrition
• They are multicellular eukaryotes lacking cell walls
• Possess specialized cells, such as muscle and nerve cells
• Characterized by structural proteins, notably collagen
• Most reproduce sexually with developmental stages including zygote, cleavage, blastula and gastrula

Animal Classification

• Animals are a subset of eukaryotes, not all eukaryotes are animals
• All animals, however, are eukaryotes
• Choanoflagellates are not animals, but the closest living relatives
• Sponges are animals within the phylum Porifera, although they lack true tissues

Protostomes vs. Deuterostomes

• Protostomes develop the mouth first
• Deuterostomes develop the anus first

Chordate Traits

• Notochord provides a flexible support rod
• Dorsal, hollow nerve cord exists
• Pharyngeal slits or clefts develop into gills/parts of the ear/throat
• Muscular, post-anal tail exists for locomotion and balance

Animal Groups

• Porifera lack tissues, are filter feeders, and sessile
• Cnidaria exhibit radial symmetry, have true tissues, and stinging cells
• Lophotrochozoa includes flatworms, mollusks, annelids, and have diverse body plans
• Ecdysozoa undergo molting (ecdysis) and include arthropods and nematodes
• Deuterostomes include echinoderms and chordates; the anus develops first

Animal Form and Function

• Streamlined bodies in tuna, penguins, and seals are examples of convergent evolution for swimming
• Natural selection favors traits increasing survival and reproductive success
• Traits are shaped by environmental and biological constraints like surface area to volume ratio

Surface Area and Volume

• Surface area increases more slowly compared to volume as size increases
• Larger cells have less surface area relative to volume, limiting exchange efficiency
• Limited surface area reduces nutrient/waste exchange efficiency, thus limiting maximum cell size
• Cells and structures can become elongated or folded to increase surface area

Multicellularity Benefits

• Specialization of cells, tissues, and organs occurs
• Organismal size increases
• Division of labor is achieved

Multicellularity Specializations

• Specialized tissues exist, such as epithelial, connective, muscle, and nervous tissues
• Organ systems facilitate exchange, movement, and internal regulation

Body Tissues

• Epithelial tissue covers surfaces and facilitates secretion and absorption
• Connective tissue binds and supports (e.g., blood, bone, adipose)
• Muscle tissue is for movement, (skeletal, cardiac, smooth)
• Nervous tissue transmits signals

Tissue Cells

• Epithelial tissue comprises epithelial cells, such as squamous, cuboidal, and columnar cells
• Connective tissue contains fibroblasts, chondrocytes (cartilage), osteoblasts (bone), adipocytes (fat), and blood cells (erythrocytes, leukocytes, platelets)
• Muscle tissue consists of muscle fibers, like skeletal, cardiac, and smooth muscle cells
• Nervous tissue includes neurons and glial cells

Tissue Molecules

• Epithelial cells have keratin, actin, and various membrane proteins
• Connective tissue cells consist of collagen, elastin, proteoglycans, and glycoproteins
• Muscle cells contain actin, myosin, tropomyosin, and troponin
• Nervous cells contain neurotransmitters, ion channel proteins, myelin (lipid-rich), and structural proteins like neurofilaments

Tissue Functions

• Tissues provide barrier, support, movement, and communication

Homeostasis

• Homeostasis is the maintenance of a relatively constant internal environment
• Examples include body temperature, blood sugar, pH, and hormone levels
• Feedback loops are systems that maintain homeostasis by responding to changes

Feedback

• Negative feedback returns a variable to a set point, such as temperature regulation via the hypothalamus, and counteracts a change
• Positive feedback amplifies a response and is less common

Adaptation vs. Acclimation

• Adaptation is an evolutionary change in a population
• Acclimation is an individual physiological adjustment

Heat Generation

• All animals generate heat through metabolic processes, amount and retention differ
• Endotherms generate and retain more heat than ectotherms
• Ectotherms rely on external heat sources, while endotherms use metabolic heat (countercurrent exchange) primarily

Endotherms vs. Ectotherms

• Endotherms have higher metabolic rates and energy needs
• Ectotherms need less energy and can survive on fewer resources, using metabolic heat

Countercurrent Exchange

• Countercurrent exchange transfers heat from warm arteries to cooler veins
• This preserves core temperature in extremities

Energy Use

• A shrew uses more energy per unit of body mass compared to an elephant
• This is because a higher surface area to volume ratio causes greater heat loss, requiring more energy for thermoregulation

Nutrition and Digestion

• Ingestion is eating/feeding
• Digestion is breaking down food into molecules small enough to absorb
• Intracellular digestion involves food vacuoles fusing with lysosomes containing digestive enzymes
• Extracellular digestion involves mechanical (e.g., chewing) and chemical breakdown (e.g., enzymes)

Nutrients

• Nutrients provides chemical energy for cellular processes
• Nutrients provides organic building blocks such as organic carbon and nitrogen
• Essential nutrients such as amino acids, fatty acids, and vitamins are required materials that from organic material

Macronutrients

• Carbohydrates are broken down by amylase in the mouth and small intestine and provide energy (glucose)
• Proteins are broken down by pepsin in the stomach and enzymes in the small intestine, building and repairing tissues, enzymes
• Fats are emulsified by bile in the small intestine, providing long-term energy storage and cell membranes

Micronutrients

• Vitamins are organic and fat- or water-soluble
  • Fat-soluble vitamins are A, D, E, K
  • Water-soluble vitamins are C and B-complex vitamins
• Minerals are inorganic, for example, calcium, iron, and potassium

Consuming Other Organisms

• Animals eat other organisms to obtain essential nutrients they cannot synthesize

Nutrient Deficiencies

• Nutrient deficiencies lead to diseases, poor immune function, stunted growth, and fatigue
  • Iron deficiency leads to weakness/anemia

Diet Adaptations

• Adaptations for ingesting different diets include dentition, length of the digestive tract, symbiotic microbes, and specialized mouthparts

Digestion

• Alimentary canals are complete digestive tracts with specialized compartments, allowing absorption in the small intestine and has 2 openings
• Gastrovascular cavities have a single opening where digestion and absorption occur in the same space, such as in cnidarians

Extracellular Digestion

• Mechanical digestion involves chewing and gut churning takes place in the mouth and stomach
• Chemical digestion involves enzymatic hydrolysis in the mouth, stomach, and small intestine
  • Amylase in saliva breaking down carbs in the mouth

Fermentative Breakdown

• Fermentative breakdown occurs with symbiotic microbes in the foregut (ruminants) or hindgut (e.g., horses)
• Animals rely on these microbes

Digestive Organs

• The liver produces bile, detoxifies blood, and regulates nutrients
• The gallbladder stores/releases bile
• The pancreas secretes digestive enzymes (exocrine) and regulates blood sugar via insulin/glucagon (endocrine)

Human Digestive system

• The path is mouth → pharynx → esophagus → stomach → small intestine (duodenum, jejunum, ileum) → large intestine (cecum, colon, rectum) → anus

Organ systems

• Head- digestion, respiration, excretion
• Lungs- respiratory
• Heart- circulatory
• Liver- digestion and excretion
• Gallbladder- digestion
• Stomach- digestion
• Pancreas- digestion and endocrine
• Kidneys- excretion
• Large instestine- digestion, excretion (water reabsorption, solid waste elimination)
• Small intestine- digestion and absorption
• Bladder- excretion
• Appendix- digestion (storage of gut bacteria)

Water and Salt Levels

• Animals regulate water and salt levels in terrestrial, freshwater, and marine environments
  • Hyperosmotic: lose water
  • hypoosmotic: gain water

Osmoconformers vs. Osmoregulators

• Osmoconformers have an internal osmolarity equal to the environment (isosmotic)

  • They don't gain/lose water and are restricted to one environment
  • E.g. marine invertebrates

• Osmoregulators maintain internal osmolarity different from surroundings

  • E.g. freshwater fish, terrestrial animals)

Osmoregulation

• Osmoregulation is control of water and solute balance to maintain homeostasis and proper cell function

Osmosis

• Water moves from low solute to high solute concentration
  • Animal cells may burst or shrink; plant cells have cell walls to buffer volume change

Osmoregulatory Adaptations

• Adaptations include kidneys, gills, salt glands, behavior (e.g., drinking water, nocturnality), concentrated urine, and impermeable skin

Changes in Osmotic Environment

• Animals adjust kidney function, hormone secretion, and ion transporter expression to changes

Salt-Excreting Glands

• Allows excretion of excess salts without large water loss (e.g., in marine birds and reptiles)

Countercurrent Exchange & Osmoregulation

• Conserves heat or solutes in extremities
• Minimizes loss by maintaining gradients (e.g., salt exchange in nasal glands)

Nitrogenous Wastes

• Nitrogenous wastes come from the breakdown of proteins and nucleic acids

Nitrogenous Forms

• Ammonia is toxic and needs water to excrete (aquatic invertebrates, freshwater fish)
• Urea is less toxic and has a moderate energy cost (mammals, amphibians)
• Uric acid is least toxic, has a high energy cost, and low water loss (birds, reptiles, insects [terrestrial])

Evolutionary History & Habitat

• Aquatic animals =ammonia; terrestrial animals = urea or uric acid

Excretion Organs

• Kidneys filter blood and form urine
• Bladder stores urine
• Large intestine reabsorbs water and compacts waste
• Anus eliminates feces

Bowman's Capsule & Filtration

• Proximal tubule: reabsorption and secretion
• Loop of Henle: water leaves descending limb; ions leave ascending limb
  • loop of henle=adaptation for dry environments, allows them to reabsorb more water and produce more concentrated urine
• Distal tubule: more reabsorption/secretion
• Collecting duct: final concentration of urine, regulated by hormones

Fluid Osmolarity Gradients

• Medulla is hyperosmotic
• Created by active transport of salts in loop of Henle, enabling water reabsorption

Kidney Filtration

• Filtered via water, salts, glucose, amino acids, nitrogenous waste (based on size/charge)
• Reabsorbed via glucose, salts, water (conserve useful substances)
• Secreted via toxins, excess ions, and drugs (remove harmful substances)

Kidney Regulation

• ADH (from pituitary): increases aquaporins in collecting duct → more water reabsorbed
• Aldosterone (from adrenal gland): increases Na+ reabsorption → water follows salt
  • Helps conserve water and raise blood pressure/volume

Water Conservation

• Uric acid excretion, salt glands, impermeable skin, behavioural changes (e.g., nocturnality)

Osmoregulation Adaptations

• Sharks retain urea, marine bony fish drink seawater and excrete salts, freshwater fish excrete dilute urine, reptiles excrete uric acid, birds use nasal salt glands

Gas Exchange

• Gas exchange occurs via diffusion across respiratory surfaces
  • Gases diffuse directly in unicellular organisms
  • Gases transport in larger animals, specialized organs (lungs, gills, skin) and circulatory systems

Circulatory Systems

• Open: hemolymph bathes organs directly, low pressure (e.g., arthropods, mollusks)
• Closed: blood confined to vessels, higher pressure and efficiency (e.g., annelids, vertebrates)

Circulation Patterns

• Single: blood passes through heart once per circuit (e.g., fish)
• Double: two circuits (pulmonary and systemic); blood passes through heart twice (e.g., mammals, amphibians)

Heart Structure

• Fish: 2-chambered heart (single circulation)
• Amphibians: 3-chambered heart (some mixing of blood)
• Mammals and birds: 4-chambered heart (complete separation of oxygenated/deoxygenated blood)

Blood Flow

• Right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body → vena cava → right atrium

Arteries vs. Veins

• Arteries carry blood away from heart with thick muscular walls
• Veins carry blood to heart, have valves to prevent backflow
• Both surrounded by connective tissue and smooth muscle

Capillary Beds

• Thin walls (single cell thick), site of gas/nutrient/waste exchange, connect arteries to veins

Blood Cells

• Red blood cells (O2 transport) (bottom layer, ~45% of blood volume)
• White blood cells (immune response) (middle layer, platelets and immune cells, ~1% of blood volume)
• Platelets (clotting)
• Plasma (top layer, 55% blood volume, mostly water and dissolved ions)
• All produced in bone marrow; production stimulated by hormones

Anemia

• Anemia causes a low red blood cell count or hemoglobin - Sickle cell anemia causes misshapen RBCs to reduce oxygen carrying capacity and can block vessels
• Sickle cell Anemia causes misshapen RBCs reduce oxygen carrying capacity and can block vessels

Animal Circulatory Structure

• Complexity and habitat varies structure
  • Aquatic animals may use gills and have simpler hearts
  • Endotherms need more efficient circulation

Water vs. Air

• Air has higher oxygen concentration and diffuses faster than water

Gills vs Lungs

• Gills: external, used in water, rely on countercurrent exchange, less efficient in air
• Lungs: internal, used in air, more efficient for terrestrial respiration

Breathing

• Breathing involves the diaphragm, lungs, and intercostal muscles.
  • The breathing rate is controlled by the brainstem and chemoreceptors sensing CO2 and pH in blood.
• Inhale: diaphragm contracts (down) and flattens/relaxes (up), thoracic cavity/diaphram expands, air drawn in
• Exhale: diaphragm relaxes, thoracic cavity volume decreases, air pushed out

Pathogens

• A pathogen is an agent that causes disease
  • Examples: viruses, bacteria, fungi, protozoa, and parasitic worms

Immune Response

• The immune system reacts to antigens, which are foreign molecules on the surface of pathogens

Innate vs. Adaptive Immunity

• Innate immunity is nonspecific, rapid, present at birth

  • Barrier defense via physical and chemical barriers.

• Celluar Defense- phagocytic immune cells that recognize pathogen fragments

• Adaptative: specific, slower response, involves memory

Innate Immune System

• Barriers (skin, mucous membranes)
• Phagocytic cells (types of white blood cells, destroy pathogens)
  • macrophages: larger phagocytic cells
  • neutrophils: destroy pathogens
  • dendritic cells: stimulate adaptive immunity
  • eosinophils: discharge enzymes
  • mast cells: inflammatory
• Natural killer cells (release chemicals)
• Inflammation, fever, antimicrobial proteins

Adaptive Immune System

• Lymphocytes
• B cells: secrete antibodies, prevent pathogen entry, originates in bone marrow
• T cells: kills pathogens, helper t cells, cytotic t cells, originate in bone marrow migrate to the thymus and activate other lymphocytes)
• Antibodies
• Memory cells

Immune System Activation

• Innate immune cells detect invaders and signal adaptive response.
• Dendritic cells present antigens to T cells.
• B cells produce antibodies.
• T cells destroy infected cells or help other immune cells

Pathogen Evasion

• Antigenic variation, secretion of immune-inhibitory proteins, hiding within host cells
• Allergies (overreaction to harmless substances), autoimmune diseases (attack on self-antigens)

Cell Identities Displayed

• MHC (major histocompatibility complex) molecules display antigens
• Antigen-presenting cells (e.g., dendritic cells) present to T cells

Antibodies

• Antibodies bind specific antigens for neutralization
  • Used in diagnostics (e.g., COVID tests), therapies (e.g., monoclonal antibodies)

Adaptive Immune Response

• Short-term: active response by effector cells
• Long-term: memory cells provide faster, stronger response upon re-exposure

Transplant Rejection

• Immune system recognizes non-self antigens and attacks grafted/transfused cells

Vaccines

• Vaccines introduce antigens to stimulate memory cell formation without causing disease
• Prevents future infections

Reproduction Types

• Asexual: produces clones, no mate needed, fast reproduction; but low genetic diversity
• Sexual: increases genetic diversity, better adaptation potential; but slower and requires more energy and a mate
• Some animals (e.g., hydra, sea anemones, certain lizards) can reproduce both ways depending on environmental conditions (e.g., stress or population density)

Sexual Reproduction

• Adaptations associated with sexual reproduction: internal fertilization and parental care
• Internal fertilization: protects gametes and embryos, allows terrestrial reproduction
• Parental care: improves offspring survival (e.g., mammals, birds)

Zygote Survival

• Fewer offspring with more care (K-strategy) leads to higher survival
• External fertilization often involves many offspring, but less care (r-strategy)

Reproductive System Structures

• Male internal: testes, vas deferens, seminal vesicles, prostate gland
• Male external: penis, scrotum
• Female internal: ovaries, oviducts (fallopian tubes), uterus, cervix, vagina
• Female external: vulva (includes labia, clitoris)

Sustentacular Cells

• Sertoli cells: support and nourish developing sperm

Interstitial Cells

• Leydig cells: produce testosterone

Gamete Production

• Spermatogenesis: continuous, millions of sperm daily, 4 sperm per cycle
• Oogenesis: begins before birth, paused at meiosis I, 1 egg per cycle, limited number of ova

Nervous System

• A brain is a centralized group of neurons that processes sensory input and coordinates responses
• It allows for faster, more complex decision-making

Nervous Systems

• CNS: brain and spinal cord, processes information
• PNS: nerves outside the CNS, carries signals to/from CNS
• Sympathetic: fight or flight (increases heart rate, dilates pupils)
• Parasympathetic: rest and digest (slows heart rate, stimulates digestion)

Neuron, Nerve, Ganglia

• Neuron: individual nerve cell
• Nerve: bundle of axons in PNS
• Ganglia: clusters of neuron cell bodies in PNS

Brain Matter

• Grey matter: neuron cell bodies; outer cortex of brain, inner spinal cord
• White matter: myelinated axons; inner brain, outer spinal cord

Human Brain

• Forebrain: cerebrum (thinking, memory), thalamus (relay), hypothalamus (homeostasis)
• Midbrain: integrates sensory information
• Hindbrain: cerebellum (coordination), pons, medulla (autonomic functions)

Reflexes

• Reflexes are automatic responses processed in the spinal cord, not the brain, for quick reaction

Mechanoreceptors

• Detect pressure, stretch, and vibration
• Involved in hearing and balance via structures like hair cells in the inner ear

Photoreceptors

• Detect light

Types of Eyes

• Simple eyes (e.g., planarians): detect light direction
• Compound eyes (e.g., insects): many lenses, detect motion well
• Camera-type eyes (e.g., vertebrates): single lens, detailed vision