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BSC Zoology - Genetics > Lecture 23 > Flashcards

Lecture 23 Flashcards

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Biology 101 flashcards
1
Q

What is the importance of the seed evolving?

A

-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

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2
Q

What were the main advancements developed in seed plants?

A

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

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3
Q

When did seed plants evolve?

A

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

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4
Q

What are the three divisions of seed plants?

A

-cycads -conifers -angiosperms (flowering plants)

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5
Q

How do cycads grow?

A

not much secondary growth, grow in columns

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6
Q

What is special about the ginko?

A

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

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7
Q

How do conifers reproduce?

A

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

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8
Q

What sort of environment do conifers need?

A

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

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9
Q

What are the four main events in land plant evolution?

A
  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).
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10
Q

What is the secondary growth?

A

• 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.

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11
Q

What are the growth rings?

A

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

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12
Q

What vessel network do the conifers have?

A

-tracheid vessels

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13
Q

What are the characteristics of pollen?

A

• 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

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14
Q

What does a seed develop from?

A
  • from fertilized ovules.
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15
Q

What is an ovule?

A

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

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16
Q

What is a sporangium?

A

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.

17
Q

How many functional spores does an ovule contain?

A

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

18
Q

Describe pollination:

A
19
Q

Describe fertilization:

A
20
Q

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

A
  • 2 years
21
Q

Describe the life cycle of a pine tree:

A
22
Q

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

A

-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!

23
Q

How are the cycads and ginko reproduced?

A

-pollinated by insects

24
Q

In which plants did these develop first:

cuticle

secondary growth

vascular cambium

pollen

xylem

stomata

sporophyte dominance

A

cuticle= mosses

secondary growth=conifers

vascular cambium=conifers

pollen=conifers

xylem=mosses

stomata=mosses

sporophyte dominance=ferns

25
Q

What is interesting about Conifers?

A
  • c.600 species of shrubs and trees
  • Tallest and longest-lived organisms
  • Ecological and biogeographic importance
  • Economic value (softwood timber, paper)
26
Q

Are conifers the oldest plants?

A

-possibly, Redwoods of california

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

27
Q

What is the history and distribution of the Southern Conifers?

A
  • 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

28
Q

What is the story with Huon pine and wollemi pine?

A
  • thought to be extinct because heavily logged
  • wollemi discovered recently that it still exists= from dinosaur ages
29
Q

What is the story of gondwana?

A

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
30
Q

How did Scott prove that antarctica was part of gondwana?

A

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

BSC Zoology - Genetics (40 decks)

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