Module 2: Organisation of Living Things
Types of organisms
Heterotrophic
Cannot produce own food
Cellular respiration
Autotrophic
Can produce own food (producers)
Photosynthesis, cellular respiration
Prokaryotic
Unicellular, no nucleus
No membrane-bound organelles
Eukaryotic
Membrane-bound organelles
Unicellular, multicellular or colonial, nucleus
Unicellular
Single cell
Every essential life process occurs in the cell
Colonial
Group of cells physically together, share resources
Each cell conducts essential life processes
Multicellular
Cells -> tissues -> organs -> organ systems -> organism
Differentiation = cells differentiate to have a particular structure
Specialisation = perform a particular function, genes on and off
Many cells; every cell still does cellular respiration
Heterotrophs
Digestive System
Absorption
Small intestine; villi increase surface area, intertwined with blood capillaries
Breakdown
Chemical; complex -> simple (enzymes in stomach, mouth, small intestine
Physical; increasing surface area (mouth, stomach)
Respiratory System
Thin and moist, large surface area, close to transport, concentration gradient
Gas exchange (oxygen in, carbon dioxide out)
Humans = alveoli
Transport System
Open = fluid not always in vessels, good for small organisms
Closed = fluid always in vessels, large and active organisms
Heart -> arteries -> arterioles -> capillaries -> venules -> veins -> heart
Transport fluid = blood or haemolymph
Delivers nutrients to cells (glucose, oxygen, minerals, amino acids, fatty acids
Removes wastes from cells (carbon dioxide, water, urea)
Autotroph Structure
Leaves
Cuticle: top layer, waxy, prevent water loss
Upper epidermis: protective, transparent (sunlight filters)
Palisade mesophyll: main site of photosynthesis, long elongated cells with chloroplasts
Spongy mesophyll: secondary site of photosynthesis, not as densely packed, air spaces for gases
Guard cells: lie on either side of the stomata, prevent water loss by opening and closing
Stomata: pores that open and close for gas exchange, some water loss (underside)
Lower epidermis: protective, has stomates and guard cells
Vein: transport bundle (xylem and phloem)
Lenticel: pores for gas exchange in woody parts, loose cells
Stem
Structural support, transport pathway
Dermal tissue: outer layer
Site of photosynthesis (provides food for the plant)
Vascular tissue: xylem, phloem
Ground tissue: all other parts
Roots
Anchor the plant, absorb water and nutrients
Central vascular bundle (xylem, phloem)
Cortex cells for storage
Root hairs increase surface area
Autotroph Processes
Xylem (water transport)
Transports water and mineral ions passively in one direction (roots -> top)
Xylem tracheid: thin, dead, hollow cells with pits (water moves across through the cells
Xylem vessel: continuous tubes, easy to flow
Transpiration
Transpiration-Cohesion-Tension Theory
Transpiration = suction pull of water from roots to leaves
Cohesion = hydrogen bonding between polar water (attraction)
Adhesion / tension = between water and xylem walls, lignin slightly polar
Factors
High temperature: increases rate, higher evaporation
High humidity: decreases, flatter concentration gradient
High wind: increases, water vapour moves away, steeper concentration gradient
High light intensity: increases, stomates more open
High water in soil: increases, larger water stream
Phloem (sugar transport)
Transports sugars up and down
Sieve tube cells: channel for products to flow through, sieve plates (join cells together)
Companion cells: alongside sieve tube cells, thought to provide energy and help with cell processes
Source to sink theory
Translocation (movement of sugars)
Source = high pressure region (sugar moves into phloem with water from xylem
Sink = low pressure region (sugar enters, water returns to xylem)
Photosynthesis
1) Light dependent
Chlorophyll absorbs light -> converts to chemical energy -> oxygen released from water
2) Light independent
Stroma in chloroplast
Thylakoid membrane of chloroplast
Carbon fixation; carbon bonds with hydrogen (glucose)
Technologies
Radioisotopes
Tag carbon dioxide with carbon isotope to track path
Measured using Geiger counter
Found by Melvin Calvin
MRI (Magnetic Resonance Imaging): radio waves + magnetic fields to form 3D image
X-Ray Computed Microtomography (Micro-CT): rotated x-ray beam to construct 3D image