A bacterial population contains heritable variations caused by mutation. When an antibiotic is used, it acts as a selection pressure. Bacteria with resistance survive and reproduce, passing resistance to progeny. Repeated antibiotic exposure increases the frequency of resistant bacteria. This fits Darwin's idea of survival and reproduction of better-adapted variants.
Antibiotic resistance is an example of natural selection: resistant variants survive antibiotic treatment and multiply, while sensitive bacteria are eliminated.
Fossil discoveries often refine evolutionary relationships. Feathered dinosaur fossils strengthen the dinosaur-bird link. Hominin fossils such as Australopithecus, Homo habilis, Homo erectus and later Homo species help reconstruct human evolution, but new finds can create debate about ancestry, dating and whether fossils represent new species or variation within known species.
Examples include discoveries of feathered dinosaurs, new hominin fossils and debates over the exact branching pattern of human evolution.
The biological species concept emphasises interbreeding and reproductive isolation. Members of the same species share a gene pool, while barriers prevent regular gene flow with other species.
A species is a group of natural populations whose members can interbreed among themselves and produce fertile offspring, and are reproductively isolated from other such groups.
Early hominins show bipedal adaptations. Later forms show larger cranial capacity, reduced jaws and canines, improved hand use and tool-making. Dietary shifts included more varied food and later cooked food. Homo habilis had larger brain and tools, Homo erectus had still larger brain and likely used fire, and Homo sapiens developed advanced language, culture and symbolic behaviour.
Human evolution involved increase in brain size and cognitive ability, upright posture and bipedal locomotion, changes in skull and jaw, use of hands for tools, changes in dentition and diet, and development of language and culture.
Mirror self-recognition and problem-solving studies suggest self-awareness in some great apes, dolphins, elephants and certain birds. However, self-consciousness can be defined in different ways, so conclusions vary depending on the test and interpretation.
Evidence suggests that some animals show forms of self-awareness, though human self-consciousness is more complex.
These examples connect living forms with fossil relatives or ancient representatives used in evolutionary study. The exact ancestor-descendant relationship may not always be direct, but each fossil helps trace evolutionary history of the modern group.
Examples: horse - Eohippus; elephant - Moeritherium; whale - Pakicetus; bird - Archaeopteryx; human - Australopithecus; camel - Protylopus; dog - Hesperocyon; rhinoceros - Hyrachyus; crocodile - Deinosuchus; turtle - Proganochelys.
For exam preparation, choose familiar examples such as fish, frog, bird, mammal, flowering plant and cactus. Label visible structures and compare homologous or analogous features where relevant to evolution.
This is a practice activity rather than a factual question. Draw and label representative plants and animals, noting features useful for comparison such as body symmetry, limbs, leaves, flowers, roots and habitat adaptations.
From an ancestral seed-eating finch, different finch species evolved on different islands with different beak shapes and feeding habits. Some became insectivorous, some seed-eating and others adapted to different resources. This diversification from a common ancestor into many forms adapted to different ecological niches is adaptive radiation.
Darwin's finches on the Galapagos Islands are an example of adaptive radiation.
Adaptive radiation refers to diversification of one ancestral stock into several species adapted to different habitats or niches, such as Darwin's finches or Australian marsupials. Human evolution involved changes through several hominin forms, but it did not produce a large range of coexisting human species specialised for many different niches in the same sense.
No. Human evolution is not usually called adaptive radiation because it is mainly a linear and branching evolutionary history within hominins, not rapid diversification into many species occupying different ecological niches from a common ancestor.
A common sequence is Eohippus/Hyracotherium -> Mesohippus -> Merychippus -> Pliohippus -> Equus. Early horses were small forest browsers with several toes. Later forms became larger, adapted to grasslands, developed longer limbs for running, reduced side toes and evolved high-crowned teeth suited for grazing.
Horse evolution can be traced from small, multi-toed ancestors such as Eohippus to modern Equus, with increase in body size, lengthening of limbs, reduction of toes and changes in teeth for grazing.