Ecology: Defensive Strategies

Defensive Strategies

• Organisms must defend themselves to survive and reproduce
• Gaboon Viper uses sit-and-wait strategy (camouflage, ambush)
• Parasites live on/in another organism; examples include micropathogens like COVID-19 and the Spanish flu.
• Parasites replicate quickly
• Attack/defense must outweigh the cost to the organism
• Bacteria have immune defenses (CRISPR-Cas9 - clustered regularly interspaced short palindromic repeats that acts by snipping out parts of viral nucleic acid)
• Animals use structural defenses like spines, thorns
• Animals use foul smells, and/or foul, oily projectiles
• Plants use constitutive (pre-formed, permanently present) and inductive defenses (exerts effect on nearby plants)
• Constitutive examples include compounds that have a negative impact on grazing insects
• Inductive examples are natural enemies of insects
• Camouflage may also be called cryptic coloration
• Poisons have to be consumed or sprayed/squirted onto exposed skin/eyes, etc
• Venoms are often introduced by a bite/sting, often resulting in a fatal outcome.
• 200 snakes are venomous out of 2,000

Defensive Strategies - Immune System

• Recognize invaders
• Mount a response to invaders
• Microbes (viruses, bacteria, and protozoa) are pathogens
• All viruses and many bacteria and protozoa replicate inside cells
• Some bacteria, protozoa, and larger parasites live outside cells
• External defenses (skin) have very tight gap junctions between cells
• Inflammatory response (increased blood supply, increased permeability of capillaries and migration of leukocytes)
• Pathogens cause inflammation
• Innate immunity is natural or native immunity, is rapid and non-specific, and lacking immunological memory.
• Natural immunity includes myeloid-line cells that originate in bone marrow.
• Soluble factors (proteins and peptides) such as the complement 30 proteins protect cells from invasion by viruses, this is made of lytic, opsonins, chemotactic and interferons
• Opsonization: macromolecules attach to the surface of microbes that phagocytes, like macrophages, recognize to increase the efficiency of phagocytosis
• Phagocytosis: process by which cells engulf and destroy large particles including bacteria, dead cells and foreign substances

Adaptive Immune Response

• Highly specific and has immunologic memory
• Strength increases with repeated exposure to pathogens
• Triggered into action by antigen presentation
• T-cells mature in the thymus gland
• Two basic types
• Helper T-cells help other cells activate their immune responses against specific pathogens.
• Cytotoxic T-cells destroy infected cells
• B-cells mature in bone marrow and produce humoral responses.
• Plasma cells produce antibodies
• Antibodies (immunoglobulins) are created.
• Memory cells provide long-lasting immunity.
• Major Histocompatibility Complex (MHC)
• MHC1: involved in cellular responses to intrinsic antigens
• MHC2: involved in humoral responses to extrinsic antigens
• Antigens are usually presented to T-cells with MHC1 or MHC2.
• Antibody types (IgG, IgM, IgA, IgD, and IgE) act in varied ways in the immune response.
• Snake antivenoms are antibodies (immunoglobins) raised in horses, and are used to neutralize venom from one species or a variety of species.

Endemic, Epidemic, Pandemic

• Endemic: a disease's constant presence in a defined geographical area (low prevalence)
• Hyperendemic: a disease's constant presence with a high prevalence in all age groups
• Novel Pathogen: enters a community without herd immunity and may be introduced accidentally.
• R0: the reproductive rate of a pathogen.
• Basis theory: susceptible to infected to recovered.
• These diseases are based on population susceptible to infection, and their chance of recovering.

Osmoregulation and Excretion

• Osmoregulation: maintains solute environment
• Regulates gain and loss of water
• Freshwater animals show adaptations reducing water uptake and conserve solutes
• Desert and marine organisms face environments that can rapidly deplete water
• Excretion: ridding of nitrogenous metabolites
• Waste products from metabolism must be excreted.
• Osmosis: diffusion across selectively permeable membranes.
• High solute concentration increases movement of water across membrane.

Excretory Systems

• Excretory are responsible for maintaining the internal environment.
• Filtration, reabsorption, secretion, and excretion are the four key functions of excretory systems.
• Systems:
• Protonephridia (network of dead-end tubules containing flame bulbs; small branches in invertebrates)
• Metanepridia (open-ended tubules; found in certain invertebrates like earthworms)
• Malpighian tubules (insects and other terrestrial arthropods) remove nitrogenous wastes from the hemolymph. They affect osmoregulation.

Nervous System

• The nervous system has three functions: sensory input, integration, and motor output.
• Neurons are nerve cells that transfer information, including dendrites (highly branched extensions that receive signals), and axons (long extensions that transmits signals).
• Ganglia are simple clusters of neurons.
• Axons transmit signals.
• Sensory information is sent to the brain.
• Motor output leaves the brain or ganglia via motor neurons.
• Action Potential: Resting to depolarization to rising phase, and falling phase, and undershoot, and refractory period.
• Synapse: a junction between neurons allowing for cell communication.
• Electrical synapses have an electrical current flowing from one neuron to the other.
• Chemical synapses have a neurotransmitter carrying information through the synapse.

Brain

• Gray matter consists of neuron cell bodies, dendrites, myelinated axons.
• White matter consists of bundles of myelinated axons.
• Peripheral nervous system (PNS) carries information into and out of the central nervous system (CNS).
• Afferent neurons bring info to the CNS
• Efferent neurons take info away from the CNS
• Brain stem coordinates and conducts info from brain centers
• Midbrain receives and integrates sensory information
• Pons regulates breathing and cardiovascular activity, and swallowing, vomiting, digestion.
• Cerebellum coordinates motor, perceptual, and cognitive functions

Endocrine System

• Chemical Messengers, called hormones, control animal growth and development.
• Hormone production usually occurs in endocrine glands.
• Hormones may be:
  • Polypeptides (water soluble)
  • Amines (water soluble)
  • Steroids (lipid soluble)
• Endocrine systems coordinate metabolic activities and environmental responses, and help with survival.
  • Many responses are controlled by multiple hormones working together to direct the function of cells in tissues, or organs. The actions of these hormones are dependent on multiple stages such as the production, release and interaction with target tissues.

Digestion

• Nutritional needs for all animals
• Biosynthesis: building molecules (for ex. essential nutrients)
• Stages of food processing:
  • Ingestion (mechanical digestion)
  • Digestion (chemical digestion - enzymatic hydrolysis)
  • Absorption (nutrient molecules enter body cells)
  • Elimination (undigested material)

Respiration

• Cellular respiration (chemical reactions that convert energy from food to usable energy)
• Respiratory organs (flatworms use body walls, fish use gills, terrestrial arthropods use tracheae, mammals use lungs.)
• Specialized surface area of organs increases gas exchange efficiency.

Circulation

• Circulatory systems provide internal transport of materials.
• Components:
  • A transport medium
  • A system of tubes (blood vessels)
  • A pump (heart)
• Open systems: blood not fully contained in vessels
• Closed systems: blood completely contained in vessels.
• Closed systems are more efficient for larger, more active animals.

Plant Physiology

• Plants used for medicine
• Chemicals found in plants may act as antioxidants, protect nutrients.
• Development and reproduction of plants.

Photosynthesis

• Autotrophs use inorganic molecules such as carbon dioxide to produce their own food
• Heterotrophs acquire organic carbon molecules from other organisms
• Photosynthesis captures light energy which is then converted to chemical energy.
• Products of photosynthesis:
  • ATP
  • NADPH
  • Glucose
• Chloroplasts contain the photosynthetic apparatus.
• Dark reaction: incorporation of CO2
• Light Reaction: electron processes, and transfer and reduction.
• Chlorophyll absorbs photons of light, which allows light to be captured.

Plant Nutrition and Transport

• Stomata: for gas exchange
• CO2 uptake is required for photosynthesis
• Transpiration is loss of water. This is also related to cooling
• Genetic adaptations to drought, or high light intensity are related to stomatal regulation and high stomatal density.
• High stomatal density is found in plants in areas with high light intensity.

Plant Hormones

• Plant hormones help regulate plant growth and development.
• Growth refers to increase of size and weight, and development describes progression of the life cycles across the different stages.
• Hormones are essential to the normal functioning of organisms
  • Cells are regulated which affects the body
  • Coordination of metabolism