Early Plant Life

Free Response

Why did land plants lose some of the accessory pigments present in brown and red algae?


Sunlight is not filtered by water or other algae on land; therefore, there is no need to collect light at additional wavelengths made available by other pigment coloration.

What is the difference between extant and extinct?


Paleobotanists distinguish between extinct species, which no longer live, and extant species, which are still living.

Describe at least two challenges that cactuses had to overcome that cattails did not.


Possible challenges include:

  • Climate: Deserts are more arid than swamps, so there is less humidity in the air and less water in the soil.
  • Reproduction: Cactuses are often not densely populated, whereas cattails occur in groups.
  • Temperature: During the day, deserts are usually hot, which increases the risk of desiccation. The desert climate will also have broader temperature ranges (extremes).

Describe a minimum of two ways that plants changed the land environment to support the emergence of land animals.


Possible examples:

  • Provided a food source
  • Increased oxygen concentration in the atmosphere
  • Provided shelter/shade from the sun
  • Provided a source of water