biology module 2

unicellular organism

An organism made up of one cell.

Multicellular organisms

Organism made up of many cells

colonial organism

a collection of similar cells living together

Volvox

a green, single-celled aquatic organism that forms minute, free-swimming spherical colonies.

Organelle

A tiny cell structure that carries out a specific function within the cell

Cell

The basic unit of structure and function in living things

Tissue

A group of similar cells that perform the same function.

Organ

A collection of tissues that carry out a specialized function of the body

organ system

group of organs that work together to perform a specific function

Specialised cells

Cells that are adapted to carry out a particular function

vascular tissue

Plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body.

Photosynthesis

process by which plants and some other organisms use light energy to convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches

cellular respiration

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

mesophyll cells

A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.

pallisade mesophyll

plant cells equipped with numerous chloroplasts and large surface areas, specialisations for photosynthesis

Cuticle

A waxy covering on the surface of stems and leaves that acts as an adaptation to prevent desiccation in terrestrial plants.

stomata

Openings in leaves to exchange photosynthetic gases: water vapor, carbon dioxide, and oxygen

gas exchange

Breathing, transport of gases, and exchange of gases with tissue cells; Provides O2 for cellular respiration and removes its waste product, CO2

Heterotrophs

organisms (animals) that obtain energy from the food the eat

Autotroph

An organism that makes its own food

pepsin

a digestive enzyme that breaks down proteins into smaller peptides and amino acids

Amylase

Enzyme in saliva that breaks the chemical bonds in starches

mechanical digestion

Physical breakdown of large pieces of food into smaller pieces

chemical digestion

Process by which enzymes break down food into small molecules that the body can use

Digestion

Breakdown of food substances into simpler forms that can be absorbed and used

stem

supporting structure that connects roots and leaves and carries water and nutrients between them

roots

Absorbs water and minerals from the ground. Anchors plant in ground.

Shoots

The aerial portion of a plant body, consisting of stems, leaves, and flowers.

Xylem

vascular tissue that carries water upward from the roots to every part of a plant

Phloem

Living vascular tissue that carries sugar and organic substances throughout a plant

open circulatory system

a type of circulation where blood (haemolymph) is not always contained within vessels but instead bathes the organs directly in body cavities.

closed circulatory system

A circulatory system in which the oxygen-carrying blood cells never leave the blood vessels

Haemolymph

the transport medium or 'blood' in insects

Arteries

carry blood away from the heart

Veins

Blood vessels that carry blood back to the heart

capillary

A tiny blood vessel where substances are exchanged between the blood and the body cells.

Haemoglobin

The protein that carries oxygen in the red blood cells.

Photoautotroph

Photosynthetic autotrophs obtain energy required for carbon fixation from sunlight.
Carbon Dioxide + Water ---> Glucose + Oxygen

Chemoautotroph

Obtain energy required for carbon fixation from inorganic chemical reactions.
Carbon Dioxide + Hydrogen ---> Methane + Water

Gas Exchange in Insects

Spiracles -> trachae -> tracheoles -> individual body cells

Gas Exchange in Fish

Water in mouth forced through gill passages -> water passes through the lamellae of the gills, dissolved oxygen diffuses into blood / carbon dioxide diffuses from blood into water at same point.

Gas Exchange in Amphibians

Breathe through moist skin (lesser extent lungs) -> oxygen captured by capillaries which are just beneath skin surface / co2 diffuses from capillaries out of skin at the same time.

Gas Exchange in Mammals

In alveoli in the lungs, oxygen diffuses across a very thing layer of cells into blood, carbon dioxide diffuses in the opposite direction.

Gas exchange in plants

Stomata open → CO₂ enters leaf → Diffuses into cells → Used in photosynthesis
Photosynthesis produces O₂ → O₂ diffuses out of cells → Exits through stomata → Released into air

transpiration-cohesion-tension theory

Water moves into the roots through osmosis, water evaporates from the plant via transpiration. Cohesive and adhesive forces draw water molecules up the xylem.

Translocation

movement of sugars from leaves to other tissues throughout the plant.

Source-Sink Model

Active transport of sugar from photosynthetic cells into phloem. Osmosis of water from xylem into phloem. Flow of sugar in all directions around plant. Active transport of sugars into non-photosynthetic cells.

Thylakoid

A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy. (Photosynthesis).