Question

1. cane toad leg length evolution

in 1935, cane toads were introduced to australia to control crop pests. they became invasive and spread rapidly. toads that had longer legs were able to travel farther and colonize new areas faster. however, this rapid movement came at a cost—longer - legged toads suffered joint damage and arthritis, reducing their survival. over time, natural selection favored shorter - legged toads, which were still able to spread but without severe injuries.
unit 7: natural selection
biology by
directions: for each example, identify and explain the trait variation with the initial advantage, describe the environmental change that took place, and identify and explain the trait variation with the advantage after the environmental change. then, interpret each graph by describing the data.

example: | variation with initial advantage | environmental change (selective pressure) | variation with advantage after environmental change | graph interpretation |

peppered moths	light moths were able to camouflage with light trees and hide from predators.	air pollution soiled light bark and turned it dark	dark moths were now able to blend in better with the environment	after the trees became dark, the # of light moths decreased in frequency and the dark moths increased in frequency
cane toads

Explanation:

For Cane Toads:

• Variation with initial advantage: Longer - legged toads could travel farther and colonize new areas faster.
• Environmental change (selective pressure): Longer - legged toads suffered from joint damage and arthritis, reducing their survival. So the selective pressure was the negative impact of long legs on survival (joint issues).
• Variation with advantage after environmental change: Shorter - legged toads were more likely to survive as they didn't have severe joint problems.
• Graph interpretation: The graph (Cane Toad Leg Length and Joint Damage) likely shows a positive correlation between leg length (x - axis) and joint damage prevalence (y - axis). As leg length increases, the percentage of toads with joint damage increases, indicating that longer - legged toads are more prone to joint damage, which supports the idea that natural selection would favor shorter - legged toads over time.

Answer:

• Variation with initial advantage: Longer - legged toads could travel farther and colonize new areas faster.
• Environmental change (selective pressure): Longer - legged toads had joint damage/arthritis, reducing survival.
• Variation with advantage after environmental change: Shorter - legged toads survived better (no severe joint issues).
• Graph interpretation: Positive correlation between leg length and joint damage prevalence (longer legs → more joint damage).