Evolution (C736)

Explanation:

Hawthorn and apple maggot flies are an example of ongoing sympatric speciation. Differences in host plant preference reduce mating opportunities between the two populations, creating prezygotic barriers. These reproductive barriers limit gene flow, making it likely that the populations will eventually become separate species. This process illustrates how ecological factors can drive speciation without geographic isolation.

Correct Answer:

Hawthorn and apple maggot flies are likely to become separate species due to increased prezygotic barriers to reproduction

Why Other Options Are Wrong:

Hawthorn and apple maggot flies have become separate species

The populations have not yet fully diverged into separate species. They still have the potential to interbreed under certain conditions, so this option overstates the current level of speciation.

Hawthorn and apple maggot flies are not in the process of speciation

There is clear evidence of reproductive isolation developing due to host plant preference, so it is incorrect to say that speciation is not occurring.

Hawthorn and apple maggot flies are likely to become separate species due to increased postzygotic barriers to reproduction

Postzygotic barriers, such as hybrid inviability or sterility, are not the main mechanism here. The primary barriers are prezygotic, arising from differences in mating timing and location associated with host plants, making this option incorrect.

Explanation:

Gill pouches observed in the embryos of chicks, humans, and house cats are examples of developmental homology. These structures appear during embryonic development and reflect shared ancestry, even though they may develop into different adult structures in each species. Developmental homologies provide evidence of evolutionary relationships and common descent, showing how similar developmental pathways can produce diverse anatomical features in related organisms.

Correct Answer:

developmental homology

Why Other Options Are Wrong:

analogy/convergent evolution

Analogous structures result from convergent evolution, where unrelated species evolve similar traits independently due to similar environmental pressures. Gill pouches are inherited from a common ancestor, not independently evolved, so this option is incorrect.

the inheritance of acquired characters

This refers to Lamarck’s discredited idea that traits acquired during an organism’s lifetime can be passed to offspring. Gill pouches are genetically inherited embryonic structures, not acquired traits, making this option incorrect.

structural homology

Structural homology refers to similarities in adult anatomical features due to common ancestry. While related, gill pouches specifically demonstrate similarities in embryonic development rather than adult structures, so developmental homology is more accurate.

Explanation:

Thomas Malthus wrote about population growth in his essay on the principle of population, noting that populations tend to grow faster than the resources available to sustain them. This results in competition for limited resources, with only some individuals surviving to reproduce. Darwin applied this concept to natural populations, which helped him develop his theory of natural selection as a mechanism for evolution.

Correct Answer:

Thomas Malthus

Why Other Options Are Wrong:

Alfred Wallace

Alfred Wallace independently conceived the idea of natural selection and co-published with Darwin, but he did not write about population growth in the 1700s, so this is incorrect.

Gregor Mendel

Gregor Mendel is known as the father of genetics for his work on inheritance in pea plants. His research was not about population growth, so this option is incorrect.

Georges Cuvier

Georges Cuvier studied fossils and extinction events and contributed to paleontology, but he did not address population growth, making this option incorrect.

Explanation:

Control variables are factors that are kept constant during an experiment to prevent them from influencing the outcome. By controlling these variables, researchers can isolate the effect of the independent variable on the dependent variable. Proper control ensures that observed changes in the dependent variable are attributable to the experimental manipulation, enhancing the validity and reliability of the results.

Correct Answer:

Control variables are important because they help ensure that the results of an experiment are due to the independent variable and not other factors.

Why Other Options Are Wrong:

Control variables are only relevant in observational studies, not in experiments.

This is incorrect because control variables are crucial in experimental design to eliminate confounding factors. Observational studies may not manipulate variables, but experiments rely heavily on controlling extraneous factors.

Control variables are the main focus of the experiment and should vary to test hypotheses.

Control variables are not meant to vary; their purpose is to remain constant so the independent variable’s effect can be accurately assessed. This option misrepresents their role.

Control variables are not necessary in experiments as they do not affect the outcome.

Ignoring control variables can introduce confounding factors that bias results. Therefore, this statement is false and contradicts basic principles of experimental design.

Explanation:

A homozygous recessive plant possesses two copies of the recessive allele for a particular trait, such as flower color. Because the recessive allele is expressed only in the absence of a dominant allele, a plant with two recessive alleles will exhibit the recessive phenotype. Therefore, the flower color of a homozygous recessive plant will be the recessive color dictated by its genotype.

Correct Answer:

The flower color will be the recessive color.

Why Other Options Are Wrong:

The flower color will be a mix of dominant and recessive colors.

A mix of dominant and recessive traits typically occurs in incomplete dominance or codominance, not in simple Mendelian inheritance where the recessive allele is only expressed in homozygotes. This option is incorrect for the scenario described.

The flower color will be determined by environmental factors.

While environmental factors can influence some traits, flower color in this example is controlled genetically by a recessive allele. Environmental influence does not override the genetic determination, so this is incorrect.

The flower color will be the dominant color.

The dominant color is expressed in individuals carrying at least one dominant allele. A homozygous recessive plant lacks any dominant allele, so the dominant color will not appear, making this option wrong.

Explanation:

A hybrid zone is a geographic region where individuals from two distinct populations or species meet and interbreed, producing offspring with mixed ancestry. Hybrid zones provide insight into the processes of gene flow, reproductive isolation, and speciation. They are important in studying evolutionary dynamics and the maintenance of species boundaries.

Correct Answer:

Hybrid zone

Why Other Options Are Wrong:

Gene flow

Gene flow refers to the transfer of alleles between populations, not specifically to the geographic area where interbreeding occurs. While hybrid zones can facilitate gene flow, the term itself describes a physical region, not the process, making this option incorrect.

Speciation

Speciation is the process by which new species arise. A hybrid zone may occur during speciation, but it is not itself the process of forming new species, so this option is incorrect.

Reproductive barrier

Reproductive barriers prevent interbreeding between populations or species. A hybrid zone, in contrast, is a location where interbreeding does occur, so this option is the opposite of the correct definition.

Explanation:

Lamarck proposed that traits acquired or modified during an organism’s lifetime could be inherited by its offspring. For example, if an organism developed a trait due to environmental pressures or behavior, that trait could be transmitted to the next generation. This concept, known as the inheritance of acquired characteristics, contrasts with Darwinian natural selection, which relies on heritable genetic variation rather than traits developed during an organism’s lifetime.

Correct Answer:

Lamarck proposed that organisms could pass on traits acquired during their lifetime to their offspring.

Why Other Options Are Wrong:

Lamarck argued that environmental changes do not affect organisms.

This is incorrect because Lamarck’s theory explicitly connected environmental changes and organismal behavior to the development of new traits. Environmental influence was central to his explanation.

Lamarck believed that natural selection was the primary driver of evolution.

Darwin, not Lamarck, formulated natural selection. Lamarck focused on acquired traits, so this option misrepresents his theory.

Lamarck suggested that all species are fixed and do not change over time.

Lamarck argued that species could change over time through acquired traits. Claiming species are fixed contradicts his main concept, making this option incorrect.

Explanation:

The dependent variable is the outcome that is measured in an experiment to assess the effect of changes in the independent variable. In the study of woodpigeons and goshawks, identifying the dependent variable allows researchers to observe how the woodpigeon's behavior changes in response to the presence of the goshawk. This provides insights into predator-prey interactions and potential evolutionary adaptations, such as behavioral changes that increase survival.

Correct Answer:

Identifying the dependent variable helps to understand how the woodpigeon's behavior is influenced by the presence of the goshawk.

Why Other Options Are Wrong:

It determines the habitat preferences of the woodpigeon

While habitat preference might be related, the dependent variable in this study specifically measures behavioral responses to the predator, not habitat selection.

It assesses the reproductive success of both species

The study is focused on behavior in response to predation, not on measuring reproductive success, so this is incorrect.

It allows researchers to measure the goshawk's hunting efficiency

The goshawk’s hunting efficiency is not being manipulated or measured as the dependent variable; the focus is on how the woodpigeons respond, making this option incorrect.

Explanation:

A hypothesis is a tentative explanation for an observation that can be tested through experimentation or further investigation. When a biologist proposes a theory without experimental support, it is considered a hypothesis because it has not yet been empirically verified. This classification allows scientists to design experiments to confirm or refute the proposed idea.

Correct Answer:

As a hypothesis

Why Other Options Are Wrong:

As a fact

A fact is an observation that has been repeatedly confirmed and is generally accepted as true. A proposed theory without experimental evidence cannot be considered a fact, making this option incorrect.

As a conjecture

Conjecture implies speculation without a basis for testing. Scientific hypotheses, even untested ones, are grounded in observation and are structured to allow empirical testing, so “conjecture” is not the proper classification.

As a scientific law

A scientific law describes a consistently observed natural phenomenon, often expressed mathematically, and is universally accepted. A theory without experimental support cannot be classified as a law, making this option incorrect.