Major Evolutionary Groups: Gymnosperms & Angiosperms (FRST 200)

Identify why were gymnosperms successful?

Heterospory: guarantees outcrossing

Reduced gametophytes: live and germinate inside sporangia

Pollen: resists desiccation and uses wind dispersal

What are living representatives of the major gymnosperm groups?

- cycad

- gnetophytes

- conifers

- gingko

- wollemia

- metasequoia

Explain where meiosis happens in gymnosperm reproduction?

During the initiation of seed cones (megasporangia) and pollen cones (microsporangia), where meiosis creates mega- and microspores that will create mega- and microgametophytes

Where are the gametophytes in conifer reproduction?

Inside sporangia

Outline the anatomy of a typical conifer seed and explain where the tissues originate from?

- Integument develops into seed coat [cone scale] (parent sporophyte 2n)

- Megagametophyte [provides nutritive tissue for embryo] (n)

- Embryo [product of fertilization- fusion of gametes] (2n)

Explain the reproductive structures inherited from gymnosperms

ovules and pollen

What structures are special to angiosperm reproduction?

- ovary (enclosing ovule)*

- fruit*

- flowers

- carpels

Identify where the gametophytes are found in a flower? What are the other structures involved in creating a flower?

ovule = megagametophyte (female)

anther = microgametophyte in pollen grain (male)

Outline the anatomy of a typical angiosperm seed and explain where the tissues originate from?

Identify the three checkpoints within the pistil that prevent fertilization from the wrong pollen?

Stigma: can prevent pollen from germinating pollen tube

Style: can prevent/stop pollen tubes from reaching the ovary

Ovule: can prevent incorrect species from depositing sperm

*if these fail, post-zygotic barriers still exist

Outline and explain at least four major trends observed in floral evolution creating diversity in flowers?

1. Tepals to developing sepals and petals

2. Floral symmetry changes from actinomorphic (radial) and zygomorphic (bilateral) symmetry

3. Free floral parts become fused flower parts (connation and adnation)

4. Superior (hyogenous) ovary becomes inferior (epigenous) or half-inferior

5. Solitary flowers become multiple (inflorescence)

Hypothesize which evolutionary trends are most likely to have been shaped through pollinator-mediated selection?

Color, shape, scent, nectar

Explain the main differences between simple, aggregate and multiple fruits?

Simple: one ovary, one flower (one pistil)

Aggregate: many ovaries, one flower (many pistils)

Multiple: many ovaries on an inflorescence

Identify key features of berries

Entire pericarp is fleshy at maturity

Identify key features of drupes

Exocarp and mesocarp are fleshy, endocarp is hardened around the seed (stone, pyrene)

Identify key features of pomes

Pericarp is fleshy, with a fleshy or leathery endocarp (core), surrounded by the hypanthium (fusion of perianth and stamens)

Identify key features of follices

many seeds in one carpel, with one suture (dehiscant)

Identify key features of legumes

many seeds in one carpel, with two sutures (dehiscant)

Identify key features of capsules

many seeds in one carpel, multiple sutures (dehiscant)

Identify key features of achenes

one seed in one carpel, free fruit wall (indehiscent)

Identify key features of cypsela

one seed, two carpels (typical of Asteraceae)

Identify key features of nuts

one seed, multiple carpels, woody pericarp often with an involucre

Outline how different means of fruit dispersal have selected for the evolution of fleshy vs. dry fruits?

fleshy: zoochory

dry: wind dispersal, adherence, mechanical ejection, water