The main challenge faced by the first land plants was access to . Plants responded to this challenge by developing . 1st blank: - Oxygen
- Water
- Sunlight

2nd blank: - Vascular tissue to transport materials throughout the plant
- Green chloroplasts
- Leaves with openings for gas exchange

The images show two species of tree frogs in a particular region. the gray tree frogs are adapted to the trees of the woodlands, while the green tree frogs can survive in woodlands or grasslands. the gray frog was abundant in the woodlands. because of climatic changes, most of the trees in the region died, and the woodlands changed to grasslands. in such a case, the . the gray tree frog is closely related to the green tree frog genetically, but they have different mating calls. this suggests that speciation occurred because of .