Biology Form 4

Contents

1. 1. Classification of Living Things: Kingdom Animalia

   1 tests 17 questions

   Topic lessons

   • Kingdom Animalia and phylum Cnidaria
   • Flatworms and roundworms
   • Annelida and Arthropoda
   • Chordata: fish, amphibians and reptiles
   • Birds, mammals and a key to vertebrates
   • Summary

   General features of kingdom Animalia Animals are multicellular eukaryotes without cell walls or chlorophyll. They are heterotrophic (mostly holozoic), most can move from place to place, they have nervous systems for fast responses, and they store food as glycogen. The kingdom is divided into phyla . Animals without a…

2. 2. Growth and Development

   1 tests 17 questions

   Topic lessons

   • Meaning and measurement of growth
   • Growth in plants
   • Structure of seeds
   • Germination
   • Growth and development in animals
   • Summary

   Meaning of growth and development Growth is a permanent, irreversible increase in size and dry mass of an organism. It happens through cell division (mitosis), cell enlargement and cell differentiation . Development is the series of changes by which an organism becomes more complex and specialised, e.g. a zygote…

3. 3. Genetics and Variation 1: Inheritance and Mendel's Laws

   1 tests 16 questions

   Topic lessons

   • Basic terms in genetics
   • DNA: structure and the genetic code
   • Cell division: mitosis and meiosis
   • Mendel and the monohybrid cross
   • Test cross, incomplete dominance and co-dominance
   • Summary

   Key terms Genetics – the study of inheritance and variation. Heredity – passing of characteristics from parents to offspring. Gene – a short section of DNA on a chromosome that controls a characteristic. Chromosome – a thread-like structure in the nucleus made of DNA and protein. Humans have 46 (23 pairs) in body…

4. 4. Genetics and Variation 2: Sex Determination, Variation and Applications

   1 tests 17 questions

   Topic lessons

   • Sex determination
   • Sex-linked inheritance
   • Inheritance of ABO blood groups
   • Variation
   • Mutation
   • Applications of genetics
   • Summary

   Sex determination Of the 23 pairs of human chromosomes, 22 pairs are autosomes and one pair are sex chromosomes . Females are XX and males are XY . All eggs carry an X; half the sperm carry X and half carry Y. So the father's sperm decides the sex of the child, and the chance of a boy or girl at each birth is 1 : 1…

5. 5. Organic Evolution

   1 tests 16 questions

   Topic lessons

   • Meaning of evolution and theories of the origin of life
   • Lamarck's theory
   • Darwin's theory of natural selection
   • Natural selection in action today
   • Evidence for evolution: fossils and comparative anatomy
   • Further evidence for evolution
   • Summary

   Meaning of organic evolution Organic evolution is the gradual change in the characteristics of populations of organisms over many generations, which can lead to the formation of new species from earlier, simpler forms. It explains the great diversity of life on Earth. Theories of the origin of life Special creation –…

6. 6. HIV and AIDS and Sexually Transmitted Infections (STIs)

   1 tests 17 questions

   Topic lessons

   • HIV, AIDS and the immune system
   • Transmission of HIV and HIV testing
   • Prevention, treatment, care and effects of HIV and AIDS
   • Sexually transmitted infections (STIs)
   • Summary

   HIV and AIDS HIV (Human Immunodeficiency Virus) is the virus that attacks the immune system. AIDS (Acquired Immune Deficiency Syndrome) is the late stage of HIV infection, when the immune system is so weak that the body cannot fight common infections. HIV attacks a type of white blood cell called the CD4 (T-helper)…