Biology

• Characteristics of Living things:

  • Movement: action causing a change of position or place
  • Respiration: chemical reactions breaking down nutrient molecules in living cells to release energy
  • Sensitivity: ability to detect stimuli and make appropriate responses
  • Growth: permanent increase in size and dry mass by an increase in cell number or size
  • Reproduction: processes that make more of the same kind of organism
  • Excretion: removal of toxic materials and waste products from organisms
  • Nutrition: taking in materials for energy, growth, and development
• Mnemonic to remember characteristics: MRS. GREN

  • Movement
  • Respiration
  • Sensitivity
  • Growth and development
  • Reproduction
  • Excretion
  • Nutrition
• Classification:

  • Species defined as a group of organisms that can reproduce to produce fertile offspring
  • Species can be classified into groups based on shared features
  • Binomial System: classification system with 2 naming parts
  • Organisms classified by Linnaeus in Latin using binomial system
  • Sequence of classification: Kingdom, Phylum, Class, Order, Family, Genus, Species
  • Genus indicates a group of related species
  • Binomial names are in italics
  • Classification aims to reflect evolutionary relationships between species
• 5 Kingdoms:

  • Animalia: multicellular, cells contain a nucleus, no cell walls or chloroplasts
  • Plantae: multicellular, cells contain a nucleus, chloroplasts, cellulose cell walls, photosynthesize
  • Fungi: usually multicellular, cells have nuclei and cell walls, feed by saprophytic or parasitic nutrition, produce spores
  • Protoctists: most are unicellular, have a nucleus, some may have cell walls and chloroplasts
  • Prokaryota: often unicellular, have cell walls and cytoplasm but no nucleus or mitochondria
• Using Dichotomous Keys:

  • Keys used to identify organisms based on a series of questions about their features
  • Dichotomous keys lead the user through to the name of the organism by giving two descriptions at a time
  • Each choice leads the user onto another two descriptions
  • Keys help in naming organisms based on shared characteristics
• Using DNA to Classify Organisms:

  • Organisms share features due to common ancestry
  • DNA sequences show evolutionary relationships between species
  • DNA sequences used to code for amino acid sequences in proteins
  • Similarities in amino acid sequences used to determine how closely related organisms are
• Animalia:

  • Main features: multicellular, cells contain a nucleus, no cell walls or chloroplasts
  • Animals feed on organic substances made by other living things
• Plantae:

  • Main features: multicellular, cells contain a nucleus, chloroplasts, cellulose cell walls
  • Plants photosynthesize
• Fungi:

  • Main features: usually multicellular, cells have nuclei and cell walls, do not photosynthesize but feed by saprophytic or parasitic nutrition
  • Fungi produce spores for survival
• Protoctists:

  • Main features: most are unicellular, have a nucleus, some may have cell walls and chloroplasts
  • Some protoctists photosynthesize while others feed on organic substances
• Prokaryota:

  • Main features: often unicellular, have cell walls and cytoplasm but no nucleus or mitochondria
• Ferns:

  • Have leaves called fronds
  • Do not produce flowers but instead reproduce by spores produced on the underside of fronds
• Flowering plants:

  • Reproduce sexually by means of flowers and seeds
  • Seeds are produced inside the ovary found at the base of the flower
  • Can be divided into two groups – monocotyledons and dicotyledons
• Monocot:

  • Flowers contain petals in multiples of 3
  • Leaves have parallel leaf veins
• Dicot:

  • Flowers contain petals in multiples of 4 or 5
  • Leaves have reticulated leaf veins, meaning they are all interconnected and form a web-like network throughout the leaf
• Structures present/absent in plant and animal cells:

  • Plant cells have a cell wall, while animal cells do not
  • Cell membrane is present in both plant and animal cells
• Plants have a cell wall that animals do not
• Magnification calculations:

  • Magnification is how many times bigger the image of a specimen observed is in comparison to the actual (real-life) size of the specimen
  • Magnification (M) can be calculated if both the size of the image (I) and the actual size of the specimen (A) are known
• Worked example:

  • An image of an animal cell is 30 mm in size and has been magnified by a factor of 3000
  • To find the actual size of the cell, divide the image size by the magnification: 30 mm / 3000 = 0.01 mm
• Units of measure:

  • Cell sizes are typically measured in micrometers (μm) or nanometers (nm)
  • All measurements in calculations must be in the same units
  • It is best to use the smallest unit of measurement given in the question
• Converting units of measurement:

  • Remember that 1 mm = 1000 μm
  • Calculate magnification by dividing the image size by the actual size
  • In the example provided, the magnification is x25
• Main difference between vertebrates and invertebrates:

  • Vertebrates have a backbone (spine)
  • Invertebrates do not possess a backbone
• There are 5 classes of vertebrates

  • Vertebrates undergo metamorphosis, changing from a larva with one body form to an adult with another
• One of the morphological characteristics used to classify invertebrates is whether they have legs or not
• All invertebrates with jointed legs are part of the phylum Arthropods
• Invertebrates are classified further into the following classes:
• Arthropods
• Other classes not specified in the text
• Mitochondria are responsible for aerobic respiration and energy production.
• The cytoplasm contains organelles such as mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, cytoskeleton, and chloroplasts (in plant cells).
• The nucleus is the control centre of the cell, containing DNA.
• The nucleus contains genetic material (DNA) that controls cell activities, including protein synthesis.
• Ribosomes are involved in protein synthesis.
• Nucleus is the control center of the cell where DNA is stored.
• Lysosomes contain enzymes that break down waste products within cells.
• Cell membrane separates the inside from outside of the cell and regulates what enters or exits the cell.
• Chromatin is made up of chromosomes that contain genetic material.
• Ribosomes synthesize proteins using information provided by mRNA.
• Nucleolus is where RNA synthesis occurs.
• Ribosome is involved in protein synthesis.