Flashcards on Organisms and the Environment

Kingdom Animalia

• Composed of Invertebrate and Vertebrate Phyla
  • Invertebrate Phyla:
    • Sponges (1st animal to evolve)
    • Cnidaria (e.g., anemone)
    • Platyhelminths
    • Molluscs
    • Arthropods (e.g., beetles, woodlice, ants, bees, butterflies), some can fly
    • Echinoderms (e.g., starfish)
  • Vertebrate Phyla:
    • Fish
    • Amphibians
    • Reptiles
    • Birds
    • Mammals
• Evolved 665 million years ago during the Cryogenian period.
• Five Groups of Life
  1. Bacteria
  2. Archaea
  3. Protists
  4. Plants
  5. Fungi
  6. Animals

Classification

• Animals are grouped based on anatomical, embryological features, and DNA.
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Organisms are also grouped by symmetry.
  • Asymmetrical: e.g., placozoans and sponges
  • Radially symmetrical: e.g., cnidarians
  • Bilaterally symmetrical: e.g., arthropods

Phylum Porifera - Sponges

• Characterized by collar cells called choanocytes
  • Asymmetrical body plan
  • No true tissues
  • Filter feeders
  • Lack respiratory organs
  • Lack reproductive organs
  • Lack a circulatory system.
  • Amoebocytes are vital cells
  • Spicules provide support but aren't a true skeleton
• Phyla with Radial Symmetry: Cnidaria and Ctenophora
  • Radial symmetry

Phylum Cnidaria

• Radially symmetrical
• Stinging tentacles
• Tissues present, but no organs
• Muscle and nerve cells present
• Life cycle includes polyp and medusoid stages
• Stinging cells called nematocytes
• Anemones possess a ciliated siphonoglyph

Phylum Mollusca

• Includes snails, slugs, clams, chitons, cephalopods, tusk shells
  • Coelomate protostomes
  • Significant diversity, with around 100,000 species.
    1. Hard calcium shell
    2. Gills
    3. Osphradium
    4. Open circulatory system
    5. Radula

Phylum Arthropoda

• Includes insects, crustaceans, bees, butterflies, flies, spiders, centipedes
  • Coelomate protostomes
  • Most diverse group, with over a million species
    • Head, thorax, and abdomen
    • Jointed exoskeleton (shed to grow)
    • Compound eyes
    • Open circulatory system
    • Tracheal system
    • Malpighian tubules

Phylum Echinodermata

• Includes starfish, sea urchins, brittle stars
  • Coelomate deuterostomes
  • Exclusively marine
    • Radial symmetry
    • No defined head
    • Oral and aboral surfaces
    • Water vascular system
    • Lacks eyes
    • Lacks circulatory or excretory systems

Phylum Chordata

• Includes non-vertebrate chordates (tunicates, cephalochordates) and vertebrates
  • Bilaterally symmetrical and coelomate
  • Notochord present at some point in life cycle
  • Myotomes
  • Dorsal nerve cord expands anteriorly to form a brain
  • Largest group= Fish. Divided into 3 groups:
    1. Agnathes: Jawless fish (hagfish and lamprey)
    2. Chondrichthyes: Cartilaginous (sharks, rays)
    3. Osteichthyes: Bony fish (lungfishes, teleosts)

Osteichthyes (Bony Fish)

• Around 20,000-25,000 species
  • Complex, articulated jaw
  • Swimbladder
  • Complex kidneys
  • Gills covered with an operculum
  • Scales
  • Lateral line
  • Lungs

Class Amphibia

• Frogs, toads, newts, salamanders
  • Skeleton adapted for terrestrial life
  • Pentadactyl limbs
  • Simple air sacs
  • Skin used in respiration
  • Require water for reproduction

Class Reptilia

• Crocodiles, snakes, lizards, turtles
  • Lungs
  • Limbs angled downwards
  • Complex kidneys
  • Salt glands
  • Internal fertilization
  • Amniote egg

Class Aves

• Approximately 10,000 species
  • Feathers
  • Adaptations for flight
  • Developed brain
  • Beak
  • Endothermic

Class Mammalia

• About 5,500 classified species
  • Hair and sweat glands
  • Milk production from mammary glands
  • Diaphragm for ventilation
  • Intelligent behavior, including learning and memory
  • Subdivided into Prototheria and Theria
    • Theria: Metatheria (marsupials) and Eutheria

Metatheria (Marsupials)

• Found mainly in Australia (434 species)
  • No placenta; development in a pouch
  • Examples: kangaroos, wallabies, koalas, wombats

Eutheria

• Found globally
  • Fetus develops in the uterus
  • Nutrients supplied via the placenta
  • Includes rodents, carnivores, ungulates, and cetaceans

Primates

• Highly evolved group of mammals
  • Binocular vision
  • Opposable thumbs
  • Large cerebral hemispheres
  • Prehensile tail (in some species)
  • Nails
  • High level of intelligence
  • Civilization

Sensitivity

• The ability to respond to the external environment is critical for survival.
  • Detection of stimuli via receptors (cells/organs like eyes, ears, nose, skin)
  • Coordination of information through nerve cells (sensory, motor, relay, spinal cord, brain)
  • Response via effectors (muscles and glands)

Amoeba

• Responds to chemicals, strong light, and mechanical stimulation
  • The cell acts as a sensory receptor
  • Withdraws pseudopodia and remains still, a basic avoidance reaction

Cnidaria

• Includes jellyfish, anemones, corals
  • Simple nerve net surrounds the entire animal; non-centralized (diffused)
  • Information weakens with distance from the stimulus

Nerve Cords

• Bundles of nerve cells with ganglia development in the anterior region (brain)

CNS - Central Nervous System

• Brain and spinal cord
  • Advantages over a nerve net:
    • Direct pathway from sensory cell to effector via coordinator or CNS
    • Nerve net is a basic plan for reflex actions

Phylum Platyhelminthes

• Defined anterior end leads movement into the environment
  • Eye spots (ocelli) are sensitive to light.
  • Auricles are sensitive to touch and act as chemoreceptors.
  • Cephalization: concentration of nerves and sensory cells in the head.
    1. Site of sensory organs
    2. Location of the brain for coordination and short pathway for information transfer
    3. Location of feeding structures
    4. Head moves into new environments first
• CNS in higher invertebrates increases organism complexity, leading to more advanced CNS as follows:
  • Receptor cells
  • Sensory nerves (afferent, towards neurons)
  • Coordinator: ganglia/brain and vertebral column
  • Motor nerves (efferent, away from neurons)
  • Effectors: muscles/glands

Phylum Mollusca, Example Octopus

• Exhibits cephalization
  • Developed head with mouth, eyes, and tentacles.
  • Brain is a series of ganglia. Nerves lead from the circumoesophageal nerve ring to the rest of the body
  • Senses chemicals, light, gravity, temperature, mechanical stimuli
  • Good eyesight
  • Capable of learning and memory

Phylum Arthropoda

• Greater cephalization with a cerebral ganglia forming the brain (supraoesophageal ganglion)
  • Three-lobed structure coordinates responses to specific sensory inputs
  • Ventral nerve runs along the insect's length, with ganglia in each segment
  • Nerves coordinate the activities of each segment
  • Flying insects have fused thoracic and abdominal ganglia
  • Detection abilities:
    • Sounds and vibration (tympanum, thin membrane across an air space)
    • Touch (hairs attached to nerves react when moved)
    • Smell (taste receptors on feet or antennae)
    • Temperature, humidity, IR radiation, Earth’s magnetic field

Phylum Chordata

• Highly developed central nervous system (CNS) and brain
  • Large brain with main sensory organs on the head
  • CNS gives rise to peripheral nerves
  • Somatic and autonomic pathways
• Brain
  • $86,000,000,000$ neurons
    • Forebrain: thalamus, hypothalamus, and cerebral cortex
    • Midbrain: reticular formation
    • Hindbrain: medulla oblongata and cerebellum

Reflexes

• Neural control via the reflex arc
  • Dorsal root contains receptor neurons
  • Ventral root contains effector neurons
  • Stimulus of receptors generates a rapid response

Sensory Receptors

1. Skin: touch, pressure, hot/cold, and pain
2. Smell and taste
3. Sight
4. Sound
5. Gravity
6. IR vision (snakes)
7. Electroreception
8. Magnetic reception

Nutrition

• The process by which organisms obtain and utilize food
  • Food provides chemical energy for metabolic reactions via respiration.
  • Raw material for growth, development, reproduction
  • Helps repair damaged cells and tissues

Animal Nutritional Requirements

1. Organic nutrients: carbohydrates, lipids, protein
2. Inorganic nutrients: minerals etc. (no C)
3. Vitamins

Types Of Nutrition

1. Autotrophic
   • Produces organic carbon from inorganic carbon
   • Examples:
     • Photoautotrophs (plants) use sunlight to convert $CO_2$ into sugar (photosynthesis).
     • Chemoautotrophs (bacteria) use inorganic compounds to produce sugar.
2. Heterotrophic
   • Obtains organic carbon from other sources (e.g., consumes organic carbon)
   • All animals
   • Types:
     • Saprotrophic:
       • Consumption of dead organic matter (decomposers)
       • Extracellular digestion: enzymes released, soluble nutrients absorbed.
       • Fungi, bacteria, and unicellular organisms are saprophytes.
     • Parasitic
       • Feeding on or within a host
       • Live on (ecto-) or within (endo-) a host
       • Causes harm to host, requires specialized morphological adaptations
       • Common to insects, leeches, platyhelminthes (e.g., tapeworm)
       • Tapeworm lacks sensory organs with hooks and suckers to cling to the intestine, absorbs food.
     • Holozoic
       • Consumption of prey whole
       • Herbivores
         • Consume autotrophs (plants)
         • Eat large amounts of plant material (low in energy, difficult to digest)
         • Produce lots of feces containing nutrients and energy
         • Specialized gut compartments (foregut + hindgut fermenters)
       • Carnivores
         • Consume heterotrophs (animals)
         • Capture and ingest prey, require highly developed sensory organs
         • Diversity of modifications to subdue prey: claws, jaws, teeth, chelipeds, fangs, beaks, venomous darts, stinging cells, sticky tongues
         • Animal protein is easier to digest and more nutritious
       • Holozoic Feeding Methods:
         • Microphagous: pseudopodia, ciliary and filter feeding
         • Macrophagous: stinging cells, detritus/deposit feeding, scraping/boring, seizing
         • Fluid feeders: sucking, biting and piercing
       • Omnivores
         • Consume both
     • Symbiotic
       • Mutualistic association between 2 organisms
3. Mixotrophic
   • Can do both

Prey Capture and Digestion

• Animals digest food without digesting themselves via specialized compartments.
• Digestion Types
  • Intracellular: within a cell via food vacuoles (food ingested by cells)
  • Extracellular: outside the cell within a specialized compartment (most animals do both)
• Cnidaria
  • Nematocytes (stinging cells) contain toxins to paralyze prey
  • Prey passes into the gastrovascular cavity
  • Enzymes released, smaller particles phagocytosed by cells lining the cavity
  • Cnidocil (hair-like structure) releases sting when brushed
  • Indigestible material rejected through the mouth (both extra- and intracellular)
• Platyhelminthes
  • Mouth extends a muscular protrusible pharynx.
  • Food taken up through the pharynx into the gastrovascular cavity.
  • Cavity is unbranched or has many lobes. Extracellular digestion is caused by enzymes that are released by cells
• Through-Gut
  • Most animals have a through-gut (mouth to anus).
  • Allows gut specialization (stomach, intestine).
  • Efficient digestion and absorption.
  • Food primarily digested extracellularly

Annelids

• Consume decaying organic matter
  • Specialized compartments along the alimentary canal:
    1. Mouth
    2. Pharynx
    3. Esophagus
    4. Crop
    5. Gizzard
    6. Intestine
    7. Anus

Molluscs

• Many contain a radula
  • Used to scrape up plant matter and break it down
  • Can produce cellulases

Arthropod

• Specialized mouthparts
  • Mastication is important
    • Mandibles have a cutting edge
  • Fore-, mid-, and hindgut
  • Symbionts in gastric caeca
  • Malpighian tubules conserve water and produce uric acid

Chemical Digestion

• Mouth
  • Amylase: enzyme in saliva that breaks down starch to maltose via hydrolysis (uses $H_2O$)
• Stomach
  • Pepsin is released by the stomach.
  • Zymogen is and inactive precursor.
• Intestine
  • Pancreas releases pancreatic amylase, lipase, trypsin, and chymotrypsin.
  • Intestinal glands release amylase, maltase, sucrase, lactase, peptidases, and lipases.
  • Bile
    • It contains NO enzymes.
    • Contains sodium hydrogencarbonate to neutralize acid and bile salts to emulsify fats.

Herbivore Fermenters

1. Foregut (cows, sheep, etc.)
   • Multi-chambered stomach
   • Anaerobic: contains bacteria + protozoa
   • Chewing the cud
   • Effective at breaking down plant material
2. Hindgut
   • (rabbits, horses etc.)
     • Symbionts found in the cecum/colon
     • Lots of material lost from the gut
     • Coprophagy: two types of feces produced

Symbiosis

• Mutualistic relationship between two organisms; both partners benefit.
  • Corals (animal) and zooxanthellae (algae)
  • Important in supplementing nutrition or assisting in digestion

Excretion

• Process by which organisms remove metabolic waste products
  1. Removal of nitrogenous wastes
  2. Regulation of water
• Various organs and waste products

Nitrogenous Waste

• Excess protein cannot be stored, is broken down in the liver
• Amino acid in the blood = amino acid pool
• Deamination produces ammonia ($NH_3$)
• Ammonia
  • Small, highly soluble but toxic compound
  • Aquatic animals produce $NH_3$ as the primary nitrogenous waste or convert it into urea or uric acid
  • Gills eliminate $NH_3$
• Ornithine cycle converts ammonia into urea, excreted by kidneys
• Uric acid produced by reptiles, insects, birds
  • Almost insoluble
  • Lack a bladder

Excretory Organs

• Evolved in animals
• Metabolic waste products must be dissolved in water to be eliminated from the body
• Waste excretion significantly impacts water balance
• Marine invertebrates lack special excretory organs
  • Waste passes directly across the gills
  • Isosmotic with seawater

Platyhelminthes

• Protonephridia (flame cells) terminate at an excretory pore
• Water and waste pass into the tubule's lumen

Annelids

• Metanephridia: Internalized tubules with a ciliated funnel (nephrostome) and external pore
  • The funnel collects coelomic fluid.
  • Some compounds are reabsorbed along the nephridium.
  • Waste is also removed from the blood

Malpighian Tubules

• Found in the gut of insects
  • Remove waste $K^+, Na^+, Cl^-$, and water from the coelom
  • Passes into the hindgut. Water and ions are reabsorbed, creating uric acid

Vertebrate Kidney

• Osmoregulation occurs in the kidney
  • Composed of many nephrons
  • Paired, located in the abdominal cavity
  • Important role in homeostasis
  • Blood enters via the renal artery and leaves via the renal vein.

Bowman’s Capsule

• Ultrafiltration of blood from the afferent arteriole into Bowman's capsule
• High blood pressure (5.92 kPa) assists filtration
• Glomerular filtrate is the same as blood plasma minus the large proteins