100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Seeded Plants £5.99   Add to cart

Lecture notes

Seeded Plants

 2 views  0 purchase

Lecture notes on Seeded plants (gymnosperms and angiosperms)

Preview 2 out of 7  pages

  • September 19, 2023
  • 7
  • 2021/2022
  • Lecture notes
  • Neil gosling
  • All classes
All documents for this subject (13)
avatar-seller
aiswaryamenon
Lecture 1: Gymnosperms

Spermatophyta (seed plants) can be divided into 2 groups

Gymnosperms - cone-bearing plants with unenclosed ovules (naked seeds)
Angiosperms - flowering plants with seeds enclosed in carpels (vessel seeds)
For both of them, the gametophytes are microscopic

Why have seed plants become dominant through evolution?
Embryo and food supply (endosperm) is surrounded by a protective coat, protecting it from UV
radiation and damage. This creates a greater chance that the seed will successfully be transferred
further.

Seeds can also retain viability for centuries - cereal and wheat - 200 year old seed
Lifecycle modifications in seed bearing plants
 Heterospory (ensures cross fertilisation)
 Gametophyte reduction and protection (protected within sporophytic plant)
 Retention of female gametophyte on sporophyte
 Pollination (gives independence from free water)
 Seed habit: embryo, endosperm and testa
Evolution towards gametophyte reduction

Gymnosperms have a pollen cone (which produces pollen) and the ovulate cone (which produces
the ovules)
Angiosperms have ovules

What are the advantages of gametophyte miniaturisation?
Gametophytes develop within sporophytes
 Moist environment prevents desiccation
 Protection from UV
 Nutrients supplied by sporophyte

Seed plants are heterosporous. Seedless plants have one kind of spore which gives rise to a bisexual
gametophyte.
Megasporangia form megaspores - female gametophytes
Microsporangia form microspores - male

Closest relative of seed plants are homosporous suggesting that heterospory evolved from
homosporous ancestors

Production of eggs by seed plants

Protecting the egg is critical for the plants reproduction.

, 8 nuclei and 7 cells.
Integuments are sporophyte tissue that envelopes the megasporangium
Gymno - 1 integument
Angio - 2

Formation of microsporangium

Seedless plants use diff mechanism to seeded ones
Mosses and fern produce flagellated sperm, requires an aqueous env-- vulnerable to drought

In seed plants, the microspore develops into a pollen grain.
Seed plants:
 Non flagellated sperm
 Use wind/animals to move
 Travel vast distances
 Survive for long periods

Seedless plants:
 Flagellated sperms
 Require aqueous env
 Travel a few cm
 Sensitive to desiccation
Ginko and cycads retain flagellated sperms but most gymnosperms are non flagellated.

Advantages of seeds over spores
Spores:
 Survive is local env isn't favourable
 Single cell so susceptible
 No nutrient supply
Seeds
 Survive for long periods
 Multicellular with protective coat
 Nutrient supply

Evolution of gymnosperms - late Devonian period - some plants acquired characteristics of seed
bearing plants (Archaeopteris)
They were heterosporous, wood forming, fern like leaves, up to 30m tall but no seeds.
Therefore these were referred to a progymnosperm - transitional species (interesting from an
evolutionary perspective)

Seed plant evolution

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller aiswaryamenon. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for £5.99. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

79373 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now

Start selling
£5.99
  • (0)
  Add to cart