Grade 10 Life Sciences: Biodiversity, Classification, History of Life, and Biomes

Comprehensive practice flashcards covering South African biodiversity, taxonomy, the five kingdoms, history of life on Earth, fossilization, human evolution, biomes, abiotic factors, and ecosystems based on the Grade 10 Life Sciences curriculum.

What is biodiversity, and what are its three distinct types?

Biodiversity is the variety of life forms that occur on Earth. Its three types are: (1) Species diversity, which is the variety of species in an area; (2) Genetic diversity, which is the genetic variation within a species; and (3) Ecosystem diversity, which is the variety of ecosystems in an area.

Which geographical and environmental factors explain why South Africa is exceptionally rich in biodiversity?

South Africa has a high-lying plateau; it lies between two very different oceans; the warm Agulhas/Mozambique current affects the east coast; the cold Benguela current affects the west coast; and different climates, rainfall patterns, and landscapes support different organisms.

How do indigenous, exotic/alien, endemic, and invasive alien species differ from one another?

Indigenous species occur naturally in a particular country or region. Exotic/alien species do not occur naturally in an area but have been introduced deliberately or accidentally. Endemic species occur naturally in only one particular country or region and nowhere else in the world. Invasive alien species are alien species that spread and negatively affect the environment, economy, or other organisms.

What are three examples of endemic species found in South Africa?

The Cape sugarbird, the riverine rabbit, and the disa plant.

What is a biodiversity hotspot, and what are the three recognised hotspots in South Africa?

A biodiversity hotspot is an area with a high level of biodiversity and a large number of endemic species. South Africa's three recognised hotspots are: (1) Cape Floral Region, (2) Succulent Karoo, and (3) Maputaland-Pondoland-Albany.

What is the difference between taxonomy and a taxon?

Taxonomy is the scientific system or study of naming and classifying organisms, whereas a taxon (plural: taxa) is a group of organisms at any level of classification.

What are the seven taxonomic categories listed in order from broadest to most specific?

Kingdom, Phylum (animals) / Division (plants), Class, Order, Family, Genus, and Species.

What three trends occur as you move from Kingdom down to Species in classification?

The number of organisms in each group decreases, the organisms become more similar, and the classification becomes more specific.

Who developed the binomial naming system, and what are its key formatting rules?

Developed by Carl Linnaeus. Each organism receives a two-part scientific name consisting of the Genus name (starts with a capital letter) and the Species name (starts with a lowercase letter). Both words are written in italics when typed (for example, Homo sapiens).

Who proposed the five-kingdom classification system in $1969$, and what are the five kingdoms?

Robert Whittaker proposed the system. The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia.

What are the distinguishing characteristics of Kingdom Monera?

Monerans are unicellular, prokaryotic (having no true nucleus), have a cell wall, reproduce asexually by binary fission, and can be autotrophic or heterotrophic (most are heterotrophic).

What are the primary characteristics of Kingdom Protista?

Protists are eukaryotic, mostly unicellular (although some algae are multicellular), mostly reproduce asexually, often live in moist or aquatic environments, and include autotrophs (such as algae) and heterotrophs (such as protozoa).

What are the major characteristics of Kingdom Fungi regarding cell structure, nutrition, and reproduction?

Fungi are eukaryotic, have cell walls made of chitin, lack chlorophyll, and are heterotrophic (mostly saprophytic, feeding on dead organic matter, while some are parasitic). Yeasts are unicellular, while mushrooms and moulds are multicellular. They reproduce using spores or other methods.

What are the distinguishing characteristics of Kingdom Plantae?

Plants are multicellular, eukaryotic, have cell walls made of cellulose, possess chlorophyll, are mostly autotrophic and make food through photosynthesis, and can reproduce sexually and asexually.

What are the defining characteristics of Kingdom Animalia?

Animals are multicellular, eukaryotic, have no cell walls, have no chlorophyll, are heterotrophic (depend on other organisms for food), are usually capable of movement, and mostly reproduce sexually.

How do prokaryotic cells differ fundamentally from eukaryotic cells?

Prokaryotic cells have no true nucleus, their DNA is free in the cytoplasm, and they lack true membrane-bound organelles (example: bacteria). Eukaryotic cells have a true nucleus with DNA enclosed by a nuclear membrane and possess membrane-bound organelles (examples: plants, animals, fungi, and protists).

What was the Cambrian explosion?

A relatively short period in geological history during the Cambrian period during which early forms of most major animal groups appeared, resulting in a rapid increase in the diversity of animal life in the fossil record.

What three conditions are necessary for fossilisation to occur?

(1) Rapid burial under sediment after death; (2) Anaerobic conditions (little or no oxygen) to reduce decomposition; and (3) The presence of hard body parts such as bones, shells, and teeth.

What are the seven steps in the formation, exposure, and discovery of a fossil?

1. An organism dies; 2. It is rapidly buried under sediment; 3. Soft tissues decay, leaving hard parts; 4. Minerals replace or harden the remaining material; 5. More sediment builds up and forms sedimentary rock; 6. Earth movements may bring the rock layers closer to the surface; 7. Erosion or human activity exposes the fossil for discovery.

What are the four types of fossils and how is each defined?

Body fossils: Preserved remains or parts of organisms. Mould fossils: Hollow impressions left behind when an organism's hard parts decay. Cast fossils: Form when a mould is filled with minerals. Trace fossils: Evidence of an organism's activities, such as footprints and burrows.

How does radiometric dating differ from relative dating?

Radiometric dating uses radioactive isotopes that decay at a constant rate measured by half-life (e.g., carbon dating for fossils younger than about $50\,000$ years). Relative dating is based on the position of fossils in sedimentary rock layers, where older fossils are generally found in lower layers and more recent fossils in upper layers.

What is a transitional fossil, and which characteristics make Archaeopteryx an example?

A transitional fossil shows characteristics of two different groups of organisms, providing evidence of evolutionary change. Archaeopteryx is a transitional form between reptiles and birds because it had reptile features (teeth, clawed fingers, long bony tail) and bird features (feathers, wishbone).

What was the gradual evolutionary sequence of the horse over millions of years?

Hyracotherium → Mesohippus → Merychippus → Pliohippus → Equus, during which the horse became larger over time.

What are the four hominin stages in human evolution highlighted in the notes and their key traits?

Australopithecus: Bipedal primates with ape-like and human-like features. Homo habilis: Had a larger brain than Australopithecus and developed better tool-making skills. Homo erectus: Had a larger, more modern human-like body and was among the first hominins to migrate out of Africa. Homo sapiens: Appeared about $200\,000$ years ago and are associated with modern humans.

What is a living fossil, and what notable event occurred with the coelacanth in $1938$?

A living fossil is an organism that has changed very little over millions of years and still resembles its ancient ancestors (e.g., coelacanth, cycads, turtles). The coelacanth was once thought to be extinct because it was known only from fossils until a living specimen was discovered in $1938$.

What were the five major mass extinctions in Earth's history, and what took place during the Permian and Cretaceous extinctions?

The five are Ordovician, Devonian, Permian, Triassic, and Cretaceous. The Permian was the largest mass extinction, wiping out approximately $90\%$ of life. During the Cretaceous extinction, dinosaurs and marine ammonites became extinct, after which mammals became dominant.

What two main explanations are provided for the End-Cretaceous mass extinction?

1. Volcanic eruptions, which released dust and gases that affected sunlight and climate, disrupting habitats and food chains. 2. Meteorite/asteroid impact, which threw dust and debris into the atmosphere, blocking sunlight, reducing photosynthesis, and disrupting food chains.

What fossil evidence is found at Barberton, Grahamstown, and Mooirivier/Estcourt in South Africa?

Barberton (Mpumalanga): Stromatolites (fossilised photosynthetic cyanobacteria). Grahamstown (Eastern Cape): Early terrestrial plants. Mooirivier and Estcourt (KZN): Glossopteris fossils.

What fossil evidence is found in the Karoo, Ladybrand/Drakensberg/Maluti, and the Cradle of Humankind?

Karoo: Mammal-like reptiles such as Lystrosaurus and Thrinaxodon. Ladybrand, Drakensberg, and Maluti: Early dinosaur fossils. Cradle of Humankind (Gauteng): Hominin fossils, including Mrs Ples and Little Foot.

What are the six levels of ecological organisation from largest to smallest?

Biosphere → Biome → Ecosystem → Community → Population → Organism.

What are the climate, vegetation, and animal characteristics of the Savanna biome?

Warm climate with seasonal rainfall; vegetation consisting of grasses with scattered trees; animal examples include elephants, giraffes, and antelope.

What are the climate, vegetation, and animal characteristics of the Grassland biome?

Hot summers with rainfall and cold winters with frost; vegetation is mainly grasses with few trees; animal examples include wildebeest, blesbok, and blue cranes.

What are the key features of the Nama Karoo and Succulent Karoo biomes?

Nama Karoo has a semi-desert climate, very low rainfall, grasses, and small shrubs (e.g., ostriches, hares, tortoises). Succulent Karoo has a very dry climate, small succulent plants with fleshy water-storing leaves, and spring flowers (e.g., meerkats, barking geckos).

What are the distinguishing characteristics of the Fynbos biome?

Cool, wet winters and hot, dry summers; evergreen shrubs including proteas and ericas; many endemic plant species; and fire that is important for the germination of some seeds.

What are the distinguishing characteristics of the Forest and Thicket biomes?

Forests feature high rainfall, are usually frost-free, and have dense trees forming a closed canopy (e.g., yellowwood and stinkwood trees). Thicket features a variable climate, shrubs and low trees often with thorns (e.g., spekboom and Euphorbia), and animals such as elephants and kudu.

What are the three physiographic abiotic factors, and what does each mean?

Aspect: The direction a slope faces. Slope: The steepness of the land. Altitude: Height above sea level.

How do sandy, clay, and loam soils differ in terms of water retention and drainage?

Sandy soil drains quickly and holds little water; clay soil holds more water but drains poorly; loam has a balance of water retention and drainage. Humus is decayed organic matter that increases soil fertility.

How do hydrophytes, mesophytes, and xerophytes differ in their habitat adaptations?

Hydrophytes are plants adapted to aquatic environments; mesophytes are plants adapted to environments with moderate water availability; xerophytes are plants adapted to dry environments.

What are the four trophic levels in a food chain, and what is the role of decomposers?

1st trophic level: Producer (makes food through photosynthesis); 2nd trophic level: Primary consumer (feeds on producers); 3rd trophic level: Secondary consumer (feeds on primary consumers); 4th trophic level: Tertiary consumer (feeds on secondary consumers). Decomposers (bacteria and fungi) break down dead organic matter and release nutrients back into the environment.

What are the three main types of ecological pyramids, and why does energy decrease as you move up trophic levels?

Pyramid of numbers, Pyramid of biomass, and Pyramid of energy. Energy decreases up trophic levels because organisms use energy for life processes and some energy is lost as heat.

What is ecotourism, and what are its five main benefits?

Ecotourism is responsible tourism that focuses on natural environments, conservation, and benefiting local communities. Its benefits include: creating employment, generating income, encouraging conservation, educating visitors about the environment, and supporting local communities.