Course review
Review each learning objective in this topic, then open its concept explanation or question set.
Learning objective
• Variation occurs between individuals within every species • Continuous variation often results from polygenes and environmental effects • Darwin's observations of variation supported natural selection
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Learning objective
• Species can be grouped by shared morphology and structural traits • Morphological species concept is useful in fieldwork, fossils, and many plants • Sexual dimorphism and within-species variation can make morphology difficult
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Learning objective
• Binomial nomenclature gives each species a universal two-part Latin name • Genus is capitalized; species is lowercase; both are italicized or underlined • Species in the same genus share similar traits
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Learning objective
• Biological species concept defines species by interbreeding and fertile offspring • It emphasizes gene flow between members of the same species • Limits include extinct organisms, asexual species, and cases with gene flow between distinct forms
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Learning objective
• Speciation is gradual as isolated populations diverge • Populations may still be theoretically able to interbreed but cannot meet • Species boundaries can therefore be partly arbitrary
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Learning objective
• Chromosome number is usually constant within a species but varies between species • Diploid chromosome numbers are even because chromosomes occur in homologous pairs • Examples include fruit fly 8, rice 24, human 46, chimpanzee 48, and dog 78
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Learning objective
• Karyotypes show chromosome number and structure in a cell • Karyograms arrange chromosomes by length, banding pattern, and centromere position • Human chromosome 2 supports fusion from two ancestral ape chromosomes
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Learning objective
• A genome is all genetic information in an organism • Members of a species share most of their genome but differ at variants • SNPs are common single-base differences used as biological markers
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Learning objective
• Eukaryote genomes vary in size and base sequence • Between-species variation is much larger than within-species variation • Not all DNA codes for proteins
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Learning objective
• Genome size is the DNA amount in one chromosome set • Larger genome size does not necessarily mean greater organism complexity • Polyploidy can greatly increase genome size, especially in plants
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Learning objective
• Whole genome sequencing began at scale with the Human Genome Project • Current uses include evolutionary relationships, gene discovery, and pathogen research • Future uses include personalized medicine, diagnosis, disease prevention, and vaccine targets
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Learning objective
• Biological species concept does not apply well to asexual organisms • Bacteria gain diversity by mutation and horizontal gene transfer • Transformation, plasmids, and recombination blur bacterial species boundaries
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Learning objective
• Diploid and haploid chromosome numbers are usually constant within a species • Meiosis conserves chromosome number across generations • Different chromosome numbers can prevent fertile hybrids, as in mules
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Learning objective
• Dichotomous keys identify organisms through paired yes/no choices • Construct keys from observable features arranged in a character matrix • Local plant or animal species can be used to build and test keys
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Learning objective
• DNA barcoding identifies species using short sequences from selected genes • eDNA from habitats can be amplified by PCR and compared with databases • Barcoding is rapid and useful for damaged, partial, or hard-to-identify specimens
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