Biology by Bradford
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The subtopic in the middle and eleven tasks round it: label four diagrams, complete two tables, put a process in order and fill 53 gaps. Every standard level statement has a box; the three boxes for higher level only are dashed and badged HL, and drop off for an SL class. Type into the blanks and check them, or print it on A4, Letter or A3 with an answer key.
The chart counts the differences between human haemoglobin β and the same protein in other vertebrates. Bases in DNA or RNA, and in proteins, can be compared like this. The fewer the differences, the more two species shared an ancestor, so of these species humans are most closely related to the . Similar sequences across all of life are strong evidence of .
In selective breeding, humans rather than the environment decide which individuals reproduce: . Cabbage, kale, broccoli and cauliflower were all bred from a single wild . Most dog breeds were created in the last two hundred years, yet they vary more in size and skull shape than all the wild members of the dog family. Large evolutionary change can therefore be .
A human arm, a bat's wing and a whale's flipper do different jobs, yet they have the same bones in the same order (matched here by colour): all are limbs. The best explanation is that all three were inherited from a .
| Isolation | What stops interbreeding | Speciation it leads to |
|---|---|---|
| Geographic | a river, mountain range or sea divides the groups | |
| Behavioural | different songs or displays, so mates are not recognised | |
| Temporal | mating or flowering at different |
Both kinds of speciation need followed by divergence; they differ in whether the groups share one place. A hybrid that does form is often , like the mule, a cross of a horse and a donkey, so alleles still cannot pass from one species to the other.
| Homologous structures | Analogous structures | |
|---|---|---|
| Evolutionary origin | ||
| Function | may differ | |
| Example | the forelimbs of a bat and a whale | the wings of a bird and an insect |
| Arise by | divergence into new uses | evolution |
Neither ape can swim, so the river keeps the two populations apart and stops between them. Conditions differ on the two banks, so different traits were favoured on each side: . Over many generations the populations into two species.
When one ancestral species gives rise to many, each adapted to a different , it is an . Darwin's finches on the Galápagos are an example, their beaks suited to different foods. Using different resources, the new species can live side by side without . This happens most where ways of life are , as on new islands, and it raises biodiversity.
Evolution is change in the characteristics of a over generations. Lamarck thought that characteristics during an organism's life, such as a giraffe's neck stretched by reaching for leaves, were passed on to its offspring. Changes that are not genetic in origin are not evolution. Natural selection explains and predicts so much that it is unlikely ever to be falsified, yet it can never be formally proved: it is a .
Number the steps in order.
Splitting is the only way new species arise. It the number of species on Earth, while reduces it. A species that changes gradually over time without dividing has evolved, but this is not .
Speciation by this route is , needing no . The new plant breeds with others like it, but its offspring with either would be sterile. Many species in the knotweed and smartweed genus, , arose this way.
1234Evolution is change in the heritable characteristics of a population over generations. Lamarck thought that characteristics acquired during an organism's life, such as a giraffe's neck stretched by reaching for leaves, were passed on to its offspring. Changes that are not genetic in origin are not evolution. Natural selection explains and predicts so much that it is unlikely ever to be falsified, yet it can never be formally proved: it is a theory.
The chart counts the differences between human haemoglobin β and the same protein in other vertebrates. Bases in DNA or RNA, and amino acids in proteins, can be compared like this. The fewer the differences, the more recently two species shared an ancestor, so of these species humans are most closely related to the gorilla. Similar sequences across all of life are strong evidence of common ancestry.
In selective breeding, humans rather than the environment decide which individuals reproduce: artificial selection. Cabbage, kale, broccoli and cauliflower were all bred from a single wild species. Most dog breeds were created in the last two hundred years, yet they vary more in size and skull shape than all the wild members of the dog family. Large evolutionary change can therefore be rapid.
A human arm, a bat's wing and a whale's flipper do different jobs, yet they have the same bones in the same order (matched here by colour): all are pentadactyl limbs. The best explanation is that all three were inherited from a common ancestor.
| Homologous structures | Analogous structures | |
|---|---|---|
| Evolutionary origin | the same | different |
| Function | may differ | the same |
| Example | the forelimbs of a bat and a whale | the wings of a bird and an insect |
| Arise by | divergence into new uses | convergent evolution |
Neither ape can swim, so the river keeps the two populations apart and stops gene flow between them. Conditions differ on the two banks, so different traits were favoured on each side: differential selection. Over many generations the populations diverged into two species.
Splitting is the only way new species arise. It increases the number of species on Earth, while extinction reduces it. A species that changes gradually over time without dividing has evolved, but this is not speciation.
| Isolation | What stops interbreeding | Speciation it leads to |
|---|---|---|
| Geographic | a river, mountain range or sea divides the groups | allopatric |
| Behavioural | different courtship songs or displays, so mates are not recognised | sympatric |
| Temporal | mating or flowering at different times | sympatric |
Both kinds of speciation need reproductive isolation followed by divergence; they differ in whether the groups share one place. A hybrid that does form is often sterile, like the mule, a cross of a horse and a donkey, so alleles still cannot pass from one species to the other.
When one ancestral species gives rise to many, each adapted to a different niche, it is an adaptive radiation. Darwin's finches on the Galápagos are an example, their beaks suited to different foods. Using different resources, the new species can live side by side without competing. This happens most where ways of life are vacant, as on new islands, and it raises biodiversity.
Speciation by this route is abrupt, needing no geographical isolation. The new plant breeds with others like it, but its offspring with either parent would be sterile. Many species in the knotweed and smartweed genus, Persicaria, arose this way.