Phylogenies, Climate, and Ecology

Which statement best defines a phylogeny?

• A diagram of gene sequences within a single organism

• The evolutionary history of a group of organisms

• A measure of genetic distance between two alleles

• The geographic distribution of species over time

Answer explanation

A phylogeny represents the evolutionary history of a group of organisms, illustrating their relationships and lineage over time, making this the best definition among the options provided.

Tags

NGSS.MS-LS4-2

In a phylogenetic tree, which part represents the most recent common ancestor where a branch splits?

• Root

• Tip (terminal node)

• Node

• Branch

Answer explanation

In a phylogenetic tree, a node represents the most recent common ancestor where a branch splits. It indicates the point of divergence between different lineages, making 'Node' the correct answer.

Tags

NGSS.MS-LS4-2

A researcher wants to determine whether a trait is ancestral or derived in a group of species. Which approach from phylogenetics is specifically used to help make this determination?

• Comparing only sister taxa

• Using an outgroup

• Measuring branch lengths in years

• Collapsing polytomies into dichotomies

Answer explanation

Using an outgroup allows researchers to identify which traits are ancestral by comparing the traits of the outgroup species to those of the ingroup species, helping to determine the evolutionary history of the traits.

Which classification describes a group that includes an ancestor and all of its descendants?

• Monophyletic (clade)

• Paraphyletic

• Polyphyletic

• Synapomorphy

Answer explanation

A monophyletic group, or clade, includes an ancestor and all of its descendants, making it the correct classification. In contrast, paraphyletic groups exclude some descendants, and polyphyletic groups do not include the common ancestor.

Tags

NGSS.MS-LS4-2

A researcher groups "warm-blooded animals" (birds and mammals) together despite lacking a recent common ancestor. What type of group is this, and which concept best justifies avoiding such groupings when estimating phylogenies?

• Paraphyletic; homoplasy

• Polyphyletic; parsimony

• Monophyletic; homology

• Polyphyletic; synapomorphy

Answer explanation

The grouping of warm-blooded animals is polyphyletic as it includes species without a recent common ancestor. Parsimony, which favors the simplest explanation, justifies avoiding such groupings in phylogenetic analysis.

Tags

NGSS.MS-LS4-2

Which statement best distinguishes homology from homoplasy?

• Homology is similarity due to shared ancestry; homoplasy is similarity from convergent evolution.

• Homology and homoplasy both indicate shared derived traits from a recent common ancestor.

• Homoplasy refers to traits present in the ancestor; homology refers to modified traits in descendants.

• Homology is minimized by parsimony, whereas homoplasy defines monophyletic groups.

Answer explanation

The correct choice highlights that homology arises from shared ancestry, while homoplasy results from convergent evolution, distinguishing the two concepts clearly.

Tags

NGSS.MS-LS4-2

When reading a phylogenetic tree, which guideline helps determine which two taxa are most closely related?

• Find the pair with the longest branches.

• Identify the shared most recent common ancestor.

• Choose the pair that appears side-by-side at the tips.

• Locate the pair with the greatest number of total traits.

Answer explanation

To determine which two taxa are most closely related, identify the shared most recent common ancestor. This ancestor indicates the closest evolutionary relationship, unlike branch length or side-by-side positioning.

Tags

NGSS.MS-LS4-2

In the Caribbean anoles case study, which hypothesis correctly explains the distribution of similar ecomorphs across islands?

• Ecomorphs evolved once and then dispersed to all islands.

• Ecomorphs evolved independently on each island due to convergent evolution.

• All islands inherited identical ecomorphs from a single ancestral species without further change.

• Ecomorph patterns are random and unrelated to evolutionary processes.

Answer explanation

The correct choice is that ecomorphs evolved independently on each island due to convergent evolution. This explains the similar traits among anoles on different islands despite their separate evolutionary paths.

Tags

NGSS.MS-LS4-2

Which statement best distinguishes climate from weather?

• Climate refers to long-term weather patterns such as average temperature and precipitation, while weather describes short-term atmospheric conditions.

• Climate is the daily condition of the atmosphere, while weather is the multi-decade average of temperature and precipitation.

• Climate includes only temperature, whereas weather includes precipitation and wind.

• Climate is unpredictable, while weather follows regular patterns.

Answer explanation

The correct choice clearly defines climate as long-term patterns of temperature and precipitation, while weather is about short-term atmospheric conditions, effectively distinguishing the two concepts.

Why are average temperatures highest near the equator and lowest near the poles?

• The equator receives less cloud cover than the poles.

• Solar radiation is distributed more evenly at the equator due to direct sunlight, whereas at the poles sunlight hits at an angle, reducing radiation per unit area.

• Ocean currents transport more heat to the equator than to the poles.

• The equator is closer to Earth’s core than the poles.

Answer explanation

Solar radiation is more direct at the equator, leading to higher temperatures. In contrast, sunlight strikes the poles at an angle, spreading the energy over a larger area, resulting in lower temperatures.

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NGSS.MS-ESS2-6