EVOLUTION TEST

Question 1

A4.1.1: Evolution as change in the heritable characteristics of a population
- Define evolution. ​

Answer 1

A cumulative change in the allele frequency of a population’s gene pool over successive generations

Question 2

• Distinguish between heritable and acquired characteristics.

Answer 2

Lamarck: The Traits acquired are the ones a person develops during his lifetime. Those aren’t passed from generation to generation.
Darwin: Hereditary characteristics have been present in the individual since his birth/inherited and are passed on from one generation to the next.

Question 3

What do Lamark and Darwin think about giraffes separately? (Lamarck - limbs lengthened/Darwin - genes!)

Answer 3

• The ancestors of the giraffe appeared similar to modern horses, with smaller necks and forelimbs compared to modern giraffes. Lamarckism states that the ancestors of giraffes, striving to reach the leaves of trees as an alternative source of food, were able to lengthen their necks. If such characters are inherited, the next generation of giraffes would be born with longer necks and would then stretch them further
• In contrast, the theory of evolution proposed by Charles Darwin proposed that variation within a population leads to selection pressures, which enables organisms that are better adapted to the environment to survive and pass on this advantage to future generations

Question 4

Comparing Lamarck and Darwin’s theories of evolution.

BMRC RE

Answer 4

Basis of variation
Mechanisms of change
Rate of Evolution
Concept of Fitness
Role of Environment
EXAMPLE: GIRAFFES AND MOTHS

Question 5

A4.1.2: Evidence for evolution from base sequences in DNA or RNA and amino acid sequences in proteins
- Identify the sources of evidence of evolution (6)

Answer 5

• Fossil record
• Homologous structures (divergent evolution - common ancestor)
• Vestigial structures (reflects evolutionary history/shows how species evolve, keep most of the traits that are beneficial and start to lose structures that they no longer need.)
• Selective breeding (can show lots of variation in a short period of time)
• Comparative DNA
• Observable changes (antibiotic bacteria)

Question 6

why fossil records are evidence for evolution?

Answer 6

• Fossil evidence provides a record of how creatures evolved and how this process can be represented by a ‘tree of life’, showing that all species are related to each other.

Fossils are the preserved remains of previously living organisms or their traces, dating from the distant past.
The fossil record is not complete or unbroken: most organisms never fossilize, and even the organisms that do fossilize are rarely found by humans.
Recall, fossils are often contained in rocks that build up in layers called strata, and the strata provide a sort of timeline, with layers near the top being newer and layers near the bottom being older.
Fossils found in different strata at the same site can be ordered by their positions, and “reference” strata with unique features can be used to compare the ages of fossils across locations.
Fossils document the existence of now-extinct species, showing that different organisms have lived on Earth during different periods of the planet’s history.
They can also help scientists reconstruct the evolutionary histories of present-day species.
Ex. Horses

Question 7

why comparative DNA is evidence for evolution?

Answer 7

At the most basic level, all living organism share:
- The same genetic material (DNA)
- The same, or highly similar genetic codes
- The same basic process of gene expression
These similarities indicate that all living things are descended from a common ancestor, used the genetic codes and expressed genes via transcription and translation

THE GREAT APES!!

Question 8

A4.1.3: Evidence for evolution from selective breeding of domesticated animals and crop plants
- Define selective breeding and artificial selection.

Answer 8

• Selective breeding is a form of artificial selection, whereby man intervenes in the breeding of species to produce desired traits in offspring. By breeding members of a species with a desired trait, the trait’s frequency becomes more common in successive generations.
• Artificial selection = selective breeding that is imposed by an external entity, usually humans, in order to enhance the frequency of desirable features.

Question 9

• List reasons why humans have selectively bred domesticated animals and crop plants.

Answer 9

• Selective breeding of plant crops has allowed for the generation of new types of foods from the same ancestral plant source
• Selective breeding of domesticated animals has also resulted in the generation of diverse breeds of offspring
• better quality/better yield/diseases resistance/can do…/animals that can’t cause harm (w/out horns)

Question 10

• Outline how selective breeding can lead to rapid evolutionary change.

Answer 10

• Selective breeding leads to faster change than natural selection; this is because only the selected individuals are allowed to breed together, while in natural selection there will still be some breeding between individuals with less favourable alleles
• The next gen, will have an increased frequency of the desired allele and this process will continue until the entire generation has the desired trait.

Question 11

• Explain an example of artificial selection in a crop plant.
• Explain an example of artificial selection in a domestic animal.

Answer 11

• Plants of the genus Brassica have been bred to produce different foods by modifying plant sections through artificial selection. This includes broccoli (modified flower buds), cabbage (modified leaf buds) and kale (modified leaves)
• Cows have been selectively bred across many generations to produce offspring with improved milk production
  Farmers have also targeted the breeding a cows with a mutation resulting in increased muscle mass. The resulting stock of cattle (termed Belgian Blue) have excessive bulk and produce more edible lean meat

Question 12

A4.1.4: Evidence from evolution from homologous structure
- State an example of homologous structures.
- Define vestigial structure.
- State an example of a vestigial structure.
- Define pentadactyl limb.
- List the bone structures present in the pentadactyl limb.
- Identify pentadactyl limb structures in diagrams of amphibians, reptiles, birds and mammals.
- Relate differences in pentadactyl limb structures to differences in limb function. (show how differences in structure, lead to differences in function)

Answer 12

• Homologous structures are those that are similar in shape/same ancestors, but have different function
  EX: A dolphin fin and bat wing - both pentadactyl limbs

-Vestigial structure = features that no longer serve the function they do in similar species (remnants of structures in an ancestral species that had a use for them)
EX: appendix and wisdom teeth

• Pentadactyl limb = a limb with 5 digits; includes humerus/femur, radius and ulna/tibia and fibula/carpals and tarsals, phalanges &meta c.&t.

Question 13

A4.1.5: Convergent evolution as the origin of analogous structures
- Define analogous structure.
- State an example of an analogous structure found in two species.
- Outline how convergent evolution results in analogous structures.

Answer 13

• Analogous structure = structures with similar functions, but different shapes and different origins
• EX: Wings of bats and birds
• Convergent evolution occurs when different species evolve similar biological adaptations in response to similar selective pressures. This happens when species occupy similar ecological niches.

Question 14

Divergent evolution

Answer 14

occurs when an ancestral species splits into two reproductively isolated groups, causing each group to develop different due to their respective selective pressures and natural selection.

Question 15

compare analogous and homologous structures (EEFS)

Answer 15

evolutionary basis:
example:
functionality:
structural similarity:
ancestors:

• both a result of evolution

Question 16

coevolution

Answer 16

• A process in which one species evolves in response to the evolution of another species. Two species can become completely dependent on each other for survival
• e.g., figs (needs pollination) and wasps (reproduction)

Question 17

A4.1.6: Speciation by splitting of pre-existing species
- Define speciation.
- Compare the process of speciation with that of gradual evolutionary change in an existing species.
- State the impact of speciation and extinction on the total number of species on Earth.

Answer 17

• Speciation = the evolutionary process by which new species form, where one species is split into two or more species
• Gradual evolutionary change: no barrier required/definitions/not creating another species
• Speciation: there must be a barrier for gene flow/definitions/literally creating another species!
• both require natural selection as a mechanism of change
• If the rate of speciation is higher than the rate of extinction, the number of species present will grow, and conversely, if extinction rate is higher, the number of species present will fall.

Question 18

A4.1.7: Roles of reproductive isolation and differential selection in speciation
- Define reproductive isolation.
- Outline how reproductive isolation and differential survival (adaptations) lead to speciation.

Answer 18

• Reproductive isolation = occurs when changes in the alleles and phenotypes of some individuals in a species prevent them from successfully breeding with other individuals that don’t have these changed alleles or phenotypes
• unable to merge genetic material geographical, behavioral, physiological, or genetic differences./different environment, different selection

Question 19

• Outline examples of speciation.
• Explain how reproductive isolation can maintain the divergent evolution of two separate species occupying the same habitat.

Answer 19

• The lava lizards of the Galápagos Islands are an example of this. One species is present on all the main islands of the archipelago. On six smaller islands there is a closely related but different species, formed by migration to the island and by reproductive isolation and divergence due to differential
  selection.
• CAN’T SWAP GENETIC MATERIAL

Question 20

NATURAL SELECTION PART 1

Question 21

D4.1.1— Natural selection as the mechanism driving evolutionary change.
- Define natural selection and fitness.
- Outline the process of natural selection and the resulting evolution of the population.
- Compare the reproductive success of better and less well-adapted individuals in a population.

Answer 21

• A mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce, and pass on these variations on to the next generation. (ACTS ON PHENOTYPE)
• Fitness measures an organism’s reproductive success (how well-adapted an individual is to its purpose or role)
• In order for natural selection to occur: Variation in adaptations within a species. / Overproduction of offspring. / Survival of the best adapted individuals. / Best adapted individuals reproduce more successfully.
• SO ALL OF THEIR OFFSPRING DEVELOP THESE ADAPTATIONS, AND SO THE SPECIES HAS EVOLVED.
• Better adapted individuals survive and are able to reproduce to pass on the adapted characteristic to their offspring. Less adapted individuals have a lower reproductive rate.

Question 22

• State that natural selection has operated continuously over billions of years, resulting in the biodiversity of life.
• Explain why Darwin’s evidence of evolution via natural selection resulted in a paradigm shift in the understanding of how life evolves.​

Answer 22

• NATURAL SELECTION ACTS ON HERETABLE CHARACTERISTICS
• Because resources are limited in nature, organisms with heritable traits that favor survival and reproduction will tend to leave more offspring than their peers, causing the traits to increase in frequency over generations.
• Natural selection causes populations to become adapted, or increasingly well-suited, to their environments over time.
• MEANING THAT WE ALL ORIGINATED FROM A COMMON ANCESTOR
• Immutable Species: This belief, upheld by both the scientific and religious communities, posited that species had always existed in their present forms, without any evolutionary history.

Question 23

STIPULATIONS/conditions OF NATURAL SELECTION

Answer 23

Individuals do not evolve, only whole populations do.

Evolution only works on traits in which variations exist.

Natural selection must be studied in context of the environmental conditions as the adaptive value of traits shifts as conditions change.

Natural selection is not a creative mechanism.

Question 24

FITNESS NOTES

Answer 24

• New alleles that result in phenotypes with higher adaptive values will increase in frequency as natural selection occurs
• The “fitness” of a given trait is relative to the selective pressures in its environment
• Adaptive value may change as the environment changes (PEPPERED MOTH)

Question 25

D4.1.2— Roles of mutation and sexual reproduction in generating the variation on which natural selection acts.
- Define biological variation.
- Explain why natural selection can only function if there is variation in a species.
- Outline sources of genetic variation (mutation, meiosis and sexual reproduction).
- Compare variation that results from mutation to those that is generated from sexual reproduction. (IGNORE)

Answer 25

• small differences in DNA base sequences between individual organisms within a population.
• If there was no variation within a species, then all individuals would be the same and no individual would be favoured over the other and natural selection would not take place.
• Mutations: Random errors in DNA, Errors in mitosis & meiosis, Environmental damage.
  Sexual reproduction: Mixing of alleles - Genetic recombination: new arrangements of alleles in every offspring, New combinations = new phenotypes.
• However, some mutations can influence the fitness of an organism, and these are known as beneficial or deleterious mutations.

Question 26

D4.1.3– Overproduction of offspring and competition for resources as factors that promote natural selection.
- State that species have the ability to produce more offspring than the environment can support.
- Use an example to illustrate the potential for overproduction of offspring in a population.
- Describe competition for resources as a consequence of overproduction of offspring.

Answer 26

• Many species create many more offspring than there are resources like food, water, and living space to support them.
• Darwin studied the reproduction of elephants, one of the slowest breeding land mammals, and found that if a single female survived and reproduced at the same rate, after 750 years there could be 19,000,000 descendants of this single mother.
• This creates a struggle to survive for the offspring. Those who are better able to survive then pass on their genes to their offspring. The competition that exists among offspring to limit survival of all offspring.
• Competition for food, living space, and mates leads to adaptations of individuals.

Question 27

DARWIN’S FINCHES

Answer 27

Competition usually is not a direct confrontation between two individuals.

• For example, Darwin’s finches have specially selected beaks adapted to their diets.
• These adaptations have allowed the birds to survive during dry seasons or when the food supply is limited by other things.
• Their beaks help the birds better compete with other birds and animals for the limited food supply.

Question 28

D4.1.4– Abiotic factors as selection pressures.
- Define selective pressure.
- Compare density-independent and density-dependent selective pressures.
- State example abiotic selective pressures.
- Outline how a selective pressure acts on the variation in a population.​

Answer 28

• external agents which affect an organism’s ability to survive in a given environment.
• density-dependent s.p. occur in biotic enviro./density-independent s.p. occur in abiotic enviro.
• ex: change in prey/predators/competitors vs. temperature/resource availability/precipitation
• both s.p.
• density-dependent - increases competition/density-independent - everyone has the same chance of being affected
• Selection pressures can be negative (decreases the occurrence of a trait) or positive (increases the proportion of a trait)

Question 29

D4.1.5— Differences between individuals in adaptation, survival and reproduction as the basis for natural selection.
- Define adaptation.
- Explain the effect of the selective pressure on the more and less adapted individuals in a population.
- Explain adaptation as a consequence of intraspecific competition. ​

Answer 29

• inherited characteristics of organisms that enhance their survival and reproduction in a specific environment
• some individuals are better adapted and able to survive and reproduce in the presence of the selective pressure while the less adapted do not survive and reproduce as successfully.
• Competition for food, living space, and mates leads to adaptations of individuals in order to survive - to become stronger.

Question 30

D4.1.6- Requirement that traits are heritable for evolutionary change to occur.
- Explain why only heritable characteristics can be acted upon by natural selection.

Answer 30

• natural selection is reliant on heritable traits because only they can be passed to offspring

Question 31

BIOLOGICAL SPECIES AND THE IMPORTANCE OF CHROMOSOMES

Question 32

A3.1.4— Biological species concept. According to the biological species concept, a species is a group of organisms that can breed and produce fertile offspring. Include possible challenges associated with this definition of a species and that competing species definitions exist.
- Define species according to the biological species concept.
- Describe limitations of the biological species concept, with mention of hybrids and geographical separation.

Answer 32

• A species is a group of (actual or potentially) interbreeding populations with a common gene pool that are reproductively isolated from other groups.
• a group of organisms that can breed and produce fertile offspring.

LIMITATIONS

• The concept of a species being able to interbreed cannot apply to extinct populations because their breeding patterns are often unknown. Extinct forms must usually be classified based on morphology (shape)
• Asexually reproducing organisms do not interbreed and so are assigned as species on the basis of appearance or biochemical similarities.

Question 33

• Describe limitations of the biological species concept, with mention of hybrids and geographical separation.

Answer 33

• Geographic isolation occurs when populations of a species become separated by a physical barrier
• Over time, these separated populations may evolve independently due to differences in environmental conditions, genetic drift (different forms of genes within a population), and natural selection. As they adapt to their respective environments, genetic differences can accumulate, leading to the divergence of populations and potentially the formation of new species.
• There are issues with the traditional definition of a species, based on interbreeding and producing fertile offspring; even though individuals within each population may still be capable of interbreeding, they may no longer have the opportunity to do so due to geographic barriers. As a result, reproductive isolation occurs not due to genetic incompatibility but due to physical separation.

Question 34

• Describe limitations of the biological species concept, with mention of hybrids and geographical separation.

Answer 34

• Hybrids can result from the selective breeding of what would be naturally isolated species.
• Ligers—the hybrid offspring of a lion and tiger—are the product of human intervention, and are mostly found in zoos. Male hybrids are infertile but female hybrids are sometimes fertile. By definition lions and tigers would be a considerable the same species but this is not accepted by biologists.

Question 35

A3.1.5— Difficulties distinguishing between populations and species due to divergence of non-interbreeding populations during speciation. Students should understand that speciation is the splitting of one species into two or more. It usually happens gradually rather than by a single act, with populations becoming more and more different in their traits. It can therefore be an arbitrary decision whether two populations are regarded as the same or different species.
- Define speciation.
- Explain the difficulties in distinguishing between populations and species during speciation.

Answer 35

• Gradual Change: The process of speciation often occurs gradually, with small changes accumulating over time. There is no clear point where one population becomes a distinct species, making it hard to pinpoint when speciation has occurred.
• Intermediates: During speciation, there can be intermediate populations that share characteristics of both the original and the emerging species. This blurs the lines between what is considered a separate species.
• Lack of Clear Criteria: There is no universally agreed-upon set of criteria that definitively define when one population has become a new species. Different species concepts (e.g., biological, morphological, ecological) may yield different results in different scenarios.
• geographical isolation/hybrids

Question 36

A3.1.6— Diversity in chromosome numbers of plant and animal species. Know in general that diversity exists. As an example, know that humans have 46 chromosomes and chimpanzees have 48. Students are not required to know other specific chromosome numbers but should appreciate that diploid cells have an even number of chromosomes.
- State that chromosome number is a distinguishing characteristic of a species.
- Explain why the typical number of chromosomes in a diploid cell is an even number.

Answer 36

• All eukaryotic species have at least two chromosomes. B/C of the fusion of two haploid cells during fertilization leads to diploid zygote cell.
• Chromosome numbers are even numbers because chromosomes are in pairs - one chromosome from mom and one from dad.

Question 37

• State the number of chromosomes in humans and in chimpanzees.
• Evaluate the evidence for the hypothesis that chromosome 2 in humans arose from the fusion of chromosomes 12 and 13 with a shared primate ancestor (Data-based question).

Answer 37

• humans; 46/chimpanzees; 48
• similar banding patterns/2 centromeres/There is evidence of the remains of telomeres at the fusion point of chromosomes 12 and 13 (should be at the ends but instead in the middle)
• The fusion site is really small, perhaps not fully allowing for the telomeres to fuse./The length of chimpanzee chromosomes 12 and 13 combined is not a perfect match for human chromosome 2; there is a slight overlap. The location of the centromere of chimpanzee chromosome 13 does not match that of human chromosome 2

Question 38

A3.1.13— Chromosome number as a shared trait within a species. Cross-breeding between closely related species is unlikely to produce fertile offspring if parent chromosome numbers are different.
- Explain how sexual reproduction maintains chromosome number within a species.
- Outline the mating of a donkey and a horse to produce a sterile mule as an example of cross-breeding between closely related species producing sterile offspring because of differences in parent chromosome numbers.

Answer 38

• The gametes are formed by meiosis during which the number of chromosomes are reduced to half, i.e. gametes contain haploid number of chromosomes. The male and female gametes fuse to form a zygote. In this way, meiosis maintains a chromosome number in species.
• A horse has 64 chromosomes, and a donkey has 62. The mule ends up with 63. Mules, because of the odd number of chromosomes, they can’t reproduce. Furthermore, this indicates that horses and donkeys may be closely related, but the differences in chromosome number mean that they are different species, and have cross-bred.
• side note: Organisms with different diploid numbers are unlikely to be able to interbreed (cannot form homologous pairs in zygotes). In cases where different species do interbreed, offspring are usually infertile (cannot form functional gametes). For instance, a horse (diploid = 64) and a donkey (diploid = 62) may produce an infertile mule (non-diploid = 63)