Lecture 23

Question 1

What is the importance of the seed evolving?

Answer 1

-one of the most dramatic innovations in land plant evolution -dramatic advance in evolution, protection of embryos by seeds -seed= container= embryo inside and diploid outside coating and nutrient material

Question 2

What were the main advancements developed in seed plants?

Answer 2

-wind pollination= no need to swim -secondary growth= girth increase -embryo develops partially on the parent

Question 3

When did seed plants evolve?

Answer 3

Fossil record extending back to the late Silurian (c. 420 million years)

Question 4

What are the three divisions of seed plants?

Answer 4

-cycads -conifers -angiosperms (flowering plants)

Question 5

How do cycads grow?

Answer 5

not much secondary growth, grow in columns

Question 6

What is special about the ginko?

Answer 6

another group -believed to be extincted= it was in china 17th centuryone tree only= all of them from this one today

Question 7

How do conifers reproduce?

Answer 7

-in cones segments= seeds large numbers of layer seeds juniper berries= modified cones= falvour of gin

Question 8

What sort of environment do conifers need?

Answer 8

australia too arid for evergreens usually -not much to eat in conifer forests -has to be humid -they are the world’s greatest carbon sink

Question 9

What are the four main events in land plant evolution?

Answer 9

1. Development of secondary growth - produces woody tissues 2. Produce two types of spores: megaspores (in ovules - female) and microspores (pollen - males) 3. Reproduce by seeds - female gametophyte & embryo enclosed within an ovule, which is nourished and protected on the parent plant 4. Male gametes transported in pollen, by wind in the conifers (pollination).

Question 10

What is the secondary growth?

Answer 10

• The Vascular Cambium is a meristem that produces additional (secondary) vascular tissue (xylem and phloem). • Secondary growth increases the girth of a stem by adding wood and bark. • Secondary growth is essential for development of shrubs and trees.

Question 11

What are the growth rings?

Answer 11

one ring= one year as it gets cold and hot= depends on weather, if drought etc

Question 12

What vessel network do the conifers have?

Answer 12

-tracheid vessels

Question 13

What are the characteristics of pollen?

Answer 13

• Pollen grains are transported to the ovule (female gamete) prior to sperm cell development. • Pollen are wind-blown to the female ovule. • The sperm cells do not require free water. -sticky ovules= draw in the pollen

Question 14

What does a seed develop from?

Answer 14

• from fertilized ovules.

Question 15

What is an ovule?

Answer 15

An ovule is a sporangium surrounded by a protective covering (integument).

Question 16

What is a sporangium?

Answer 16

an enclosure in which spores are formed - Sporangia can produce spores by mitosis, but in nearly all land plants and many fungi, sporangia are the site of meiosis and produce genetically distinct haploid spores.

Question 17

How many functional spores does an ovule contain?

Answer 17

-one functional spore, which is retained on the parent plant.

Question 18

Describe pollination:

Answer 18

Question 19

Describe fertilization:

Answer 19

Question 20

How long does it take for a fertlized ovule to develop into a seed?

Answer 20

• 2 years

Question 21

Describe the life cycle of a pine tree:

Answer 21

Question 22

Cycads and Gingko - what feature of their reproduction reminds us of the ferns and mosses?

Answer 22

-when the sperm reaches the surface of the egg= grows two flagella and swims last few microns to reach the nucleus

-like ferns in that they swim= but these only swim the last few microns= so need water!!! like mosses!

Question 23

How are the cycads and ginko reproduced?

Answer 23

-pollinated by insects

Question 24

In which plants did these develop first:

cuticle

secondary growth

vascular cambium

pollen

xylem

stomata

sporophyte dominance

Answer 24

cuticle= mosses

secondary growth=conifers

vascular cambium=conifers

pollen=conifers

xylem=mosses

stomata=mosses

sporophyte dominance=ferns

Question 25

What is interesting about Conifers?

Answer 25

• c.600 species of shrubs and trees
• Tallest and longest-lived organisms
• Ecological and biogeographic importance
• Economic value (softwood timber, paper)

Question 26

Are conifers the oldest plants?

Answer 26

-possibly, Redwoods of california

–look dead, older then the fungi 5000 years old!

Question 27

What is the history and distribution of the Southern Conifers?

Answer 27

• New Zealand rich in conifers, mainly podocarps and Kauri
• Australia is relatively poor in conifers because of aridity
• Australia does have a range of conifers (e.g., Kauri, Callitris, Huon pine)

• The latest Australian conifer: the Wollemi pine! • The history of Australian conifers can be traced back to
Gondwana, its breakup and resulting climate change. • How is it that we know about Gondwana and its past vegetation

-tasmania= conifers as well, mostly australia= too dry, since small groups= hard to reproduce= wind pollination

wollemi pine= new found, believed to have been extinct, living fossil

Question 28

What is the story with Huon pine and wollemi pine?

Answer 28

• thought to be extinct because heavily logged
• wollemi discovered recently that it still exists= from dinosaur ages

Question 29

What is the story of gondwana?

Answer 29

About 300 million years ago, Australia, Antarctic, S. America, Africa and S. India formed the supercontinent GONDWANA

• •
About 150 mya GONDWANA began to fragment. India and S. Africa drifted away. About 50 mya Australia separated from Antarctica - it has drifted north to its present latitude

• Australia was part of Gondwana until about 30mya.
• As Gondwana broke up, the climates and vegetation of the continents changed significantly.
• Some of Australia’s flora is an “ancient” component derived from Gondwana times (e.g., it’s southern conifers including the Wollemi Pine

Question 30

How did Scott prove that antarctica was part of gondwana?

Answer 30

scott= natural scientists, nobody believed that antarctica was an different than then= found the glosspteris fossil= proved that the gondwana was real