Seed Plants and Angiosperms Overview

Announcements and Reminders

  • RRQs 10-14 due by 12 PM (noon) on Tuesday, April 22
  • Check the links in the Videos, articles, etc. folder
  • Exam #3 will cover various taxon names and life cycles; start studying now!
  • Date: Tuesday, April 22; remember to bring pencils and erasers.
  • BMAC students: reserve your spot ASAP!

Summer Research Experience - CSULB/Catalina Island Conservancy

  • Dates: July 13-26, 2025
  • Deadline to apply: 5 PM on Friday, April 11
  • Selected applicants will be invited for interviews by April 18; in-person interviews from April 21-25 (times TBD)
  • Announcements of selected applicants will be during the week of April 28 to May 2
  • Confirmation of position acceptance due by May 9; up to two alternates; final decisions by May 14.

Guided Animal Drawing Workshop - CSULB Animal Museum

  • Location: Hall of Science, Room 074
  • Dates:
    • 02/28 - Big Skulls
    • 03/14 - Birds & Wings
    • 04/11 - Fur
  • Time: 1 PM - 3 PM
  • All skill levels and majors welcome; bring your own materials. Limited space; please RSVP at kelly.hood@csulb.edu.

Key Topics in Land Plants (Part 3)

  • Review of seed plant traits and gymnosperms:
    • Key features of angiosperms:
    • Flowers
    • Double fertilization
    • Endosperm
    • Fruits
    • Diversity and importance of angiosperms.

Seed Plant Characteristics

  • Key Traits of Seed Plants:
    • Originated from ancestral green algae.
    • Different groupings:
    • Bryophytes (nonvascular): Liverworts, Mosses, Hornworts
    • Vascular Plants:
      • Seedless: Lycophytes, Monilophytes
      • Seed plants: Gymnosperms and Angiosperms
  • Earliest fossils of seed plants date back to ~$360 million years ago, with gymnosperms appearing around $305 million years ago.

Detailed Characteristics of Seed Plants

  • Reduced Gametophytes:

    • Mosses: Gametophyte dominant
    • Ferns: Reduced independent gametophytes
    • Seed plants: Dominant sporophyte, reduced dependent gametophytes

  • Heterospory evolved multiple times in vascular plants, crucial for the common ancestor of seed plants.

Ovules and Pollen in Seed Plants

  • Ovules: Composed of the megasporangium protected by integuments.
  • Pollen: Microsporangium produces microspores encased in sporopollenin; pollen grains carry microgametophyte to ovules via pollen tubes.

Seed Development in Angiosperms

  • Seed formation:
    • At fertilization, a diploid zygote forms and develops into a dormant multicellular seed composed of three types of tissue:
    • Seed coat (from integument)
    • Nutritional female gametophytic tissue
    • Diploid embryonic sporophyte

Gymnosperms

  • Gymnosperms do not produce flowers. The seeds are exposed on cones divided into four main clades:
    • Conifers: ~600 species
    • Gnetophytes: ~90 species
    • Cycads: ~300 species
    • Ginkgos: one species

Angiosperm Traits

  • Flowers: Main synapomorphy, diverse in form with parts including sepals, petals, stamens, and carpels.
  • Key traits:
    • Double fertilization; results in formation of endosperm.
    • Importance of symmetry: radial and bilateral.

Fruit Development in Angiosperms

  • Fruits develop from the ovary wall and function to protect seeds and aid in their dispersal.
  • Types of fruits include simple, aggregate, and multiple fruits.
  • Mechanisms of seed dispersal: wind, water, and animals.

Importance of Seed Plants to Humans

  1. Ecosystem services:
    • O2 production, soil formation, soil fertility, erosion prevention.
  2. Primary producers: Crucial food source for humans and terrestrial communities, with angiosperms providing major calorie sources.
  3. Wood: Essential for construction, fuel, and paper.
  4. Medicines: Many derived from naturally occurring plant compounds.

Key Vocabulary

  • Monoecious / Dioecious
  • Inflorescence
  • Double fertilization
  • Endosperm
  • Cotyledon
  • Fruit (exocarp, mesocarp, endocarp)
  • Floral organs: sepals, petals, stamen, carpel
  • Aggregate Fruit, Multiple Fruit, Accessory Fruit

Study Questions

  1. Describe the basic structure of a flower and its floral organs.
  2. What roles do parts of a flower play in attracting pollinators?
  3. Define perfect vs. imperfect flowers; explain monoecious and dioecious plants.
  4. Differentiate between inflorescences and single flowers.
  5. Explain the angiosperm life cycle and how it compares with gymnosperms.
  6. What is the purpose of fruits in plant reproduction?