Plant Evolutionary Timeline

Question 1

What was the main hurdle plants had to overcome in order to successfully survive and breed on land?

Answer 1

When first online, gametes still needed water to reach each other. Plants were therefore not very good at surviving in areas that were not damp at the very least.

Question 2

What is the dominant group of plants today?

Answer 2

Angiosperms (flowering plants)

Question 3

In what era is life believed to have first arose? What is this life form a common ancestor of?

Answer 3

Archean; common ancestor of cyanobacteria.

Question 4

What is the important event that took place during Archean period?

Answer 4

GREAT OXYGENATION EVENT creation of free oxygen in the atmosphere from the splitting of water for electrons in photosynthesis.

Question 5

Why are cyanobacteria an important species in the evolutionary timeline?

Answer 5

Believed to be the ancestors of chloroplasts and mitochondria.

Question 6

What plant types evolved in the Ediacaran period?

Answer 6

Red and green algae.

Question 7

What happened in the Cambrian period? What happened specifically to plants?

Answer 7

Explosion of (mostly marine) life in the Cambrian period. Red and green algae came to the forefront as primary producers.

Question 8

What are embryophytes?

Answer 8

Land plants

Question 9

What plant is the ancestor of embryophytes?

Answer 9

Green algae.

Question 10

What occurred in the ordovician period?

Answer 10

a few animals and plants began to explore the margins of the land (evidenced by spores) –> first embryophytes. Majority of life still confined to the seas.

Question 11

The first spores that appeared in the Ordovician period resemble the spores of which primitive land plant?

Answer 11

The liverwort.

Question 12

What is believed to be a possible cause of the Ordovician-Silurian mass extinction?

Answer 12

The consumption of CO2 by plants.

Question 13

Which plants are Bryophytes?

Answer 13

Liverworts, hornworts and mosses.

Question 14

Which plants evolved in the Silurian period? Which habitats do we see emerging?

Answer 14

Bryophytes diversified and the first lycophytes evolved. The first river and wetland habitats appear.

Question 15

What are lycophytes?

Answer 15

Primitive vascular plants.

Question 16

What physical adaptations have emerged by the end of the Silurian period? How do they help for life on land?

Answer 16

Branching - Enables some upward growth
Vasculature - Enables movement of water
Cuticle - Prevents desiccation
Stomata - Needed for gas exchange

Question 17

What reproductive adaptations emerged by the end of the Silurian period?

Answer 17

Sporophyte becomes less dependent upon gametophyte and is moving towards dominance.

Question 18

Identify which generation is n and which is 2n in plants.

Answer 18

n = gametophyte
2n = sporophyte

Question 19

In which plants groups are gametophytes the dominant stage? Sporophytes?

Answer 19

Gametophytes = Bryophytes
Sporophyte = angiosperms and gymnosperms

Question 20

What types of plants evolve in the Devonian period?

Answer 20

Lycophytes diversify, ferns, trees and seed plants appear.

Question 21

What is important to note about the Devonian period?

Answer 21

Most adaptations required for life on land have appeared by the end of the devonian period.

Question 22

What adaptations appear in the Devonian period? How are they important?

Answer 22

Roots - Movement of water and soluble resources, adds support
Lignin - adds support, waterproofing, protection
Seeds - protection
Secondary growth/vascular cambium - longevity, adaptability, increased size
Bark - protection

Question 23

Differentiate between spores and seeds.

Answer 23

Spores = n; seeds = 2n
Seeds have seed coat to prevent desiccation and damage, enabling it to leave the plant. Spores do not leave sporangia.
Seeds contain resources to support young plant, spores do not.

Question 24

What is the state of plants in the Carboniferous period?

Answer 24

“Go mad”.
Move into drier and previously inhospitable habitats
Get large
Grew and died at such a rate the eventually became coal.

Question 25

What type of plants appear in the Carboniferous period?

Answer 25

Gymnosperms

Question 26

What happened to the atmospheric composition in the Carboniferous period?

Answer 26

Increased O2 levels (highest in Earth’s history)

Question 27

What types of plant declined in the Permian period? What plants do we see enter the fossil record?

Answer 27

Non-seed plants decline. Conifers, cycads, ginkgos enter record

Question 28

What is the environment like in the permian period? What types of adaptations does this favour?

Answer 28

Arid environment favoured adaptions that reduced water loss and/or enabled plants to survive harsh conditions in a dormant state.

Question 29

Which adaptations became especially useful during the permian period?

Answer 29

Xylem vessel-like elements
Seed dormancy and seed food reserves
More extensive root systems
Larger and more complex leaves

Question 30

In which era did the worst mass extinction occur? Which era followed

Answer 30

Permian followed by Triassic.

Question 31

What types of plants are prevalent in the Triassic period?

Answer 31

Cycads and conifers

Question 32

Which non-extants emerged in the Triassic/Jurassic periods?

Answer 32

Glossopterids and Corystopermales

Question 33

Which plants are dominant in the Jurassic period? Which ones are also common?

Answer 33

Conifers dominant, cycads, ginkgos and Cyatheales (tree ferns) common

Question 34

In which period did the angiosperms arise?

Answer 34

Cretaceous

Question 35

What happened to insects during the cretaceous period? What could this indicate?

Answer 35

Insects diversify, possibly due to coevolution with plants.

Question 36

What are distinguishing traits of angiosperms?

Answer 36

Flowers & Fruits. Simple micro- and megagametophytes
Endosperm
Ovule surrounded by two integuments. Well nearly always.
Pollen wall morphology. Two layers separated by columns
Xylem vessels. Not unique & not always present
Sieve elements with companion cells in Phloem

Question 37

Differentiate between angiosperms and gymnosperms.

Answer 37

Angiosperms: Sieve tube members have end plates. Associated with companion cells
Gymnosperms: Sieve cells have narrow ends and don’t have end plates

Question 38

What are the important emergences of the Paleogene?

Answer 38

Angiosperms becoming more diverse and dominant
C4 metabolism arises
Grasses