THE PLANT KINGDOM LIFE CYCLE OVERVIEW

Chapter 23

Basic Concepts- asexual vs. sexual reproduction(most)

1. asexual reproductiona. one individual, no diversity in

offspring, less time and Eb. asexual spores and structures

i. spores: small packets of DNA, protected by a tough outer coat

ii. mitosis diploid (2n) structures

SEXUAL REPRODUCTION

a. two individuals, diversity in offspring, more time and E

b. involves reproductive structures:i. sporangia, cones, flowersii. monoecious vs. dioecious plants• monoecious: every ind.

produces both egg and sperm• dioecious: separate male and

female individuals

Fig. 23.3 Alternation of generations

a. sexual sporesi. haploid produced through meiosisii. sporophyte phase of life cycle• plant itself is diploid (2n)

b. sexual gametesi. egg and sperm cells• haploid, but produced through

mitosisii. gametophyte phase of life cycle• plant itself is haploid (n)

Alternation of Generations-sporo. vs gametophyte

1. sporophyte generationa. diploid (2n) stageb. germ cells in reproductive

structures undergo meiosis• produce 4 haploid spores each

c. spores will grow and develop new gametophyte

d. most prominent generation in most plants

gametophyte generation

a. haploid (n) stageb. gametophyte develops from haploid

sporesc. produces gametes (egg and sperm cells)

i. special cells in specialized structuresii. mitosis

• why no need for meiosis here?d. fertilization zygote new sporophyte

• fertilization involves two different individuals of same species

e. not very prominent in most plants

Fig. 27.1Alternation of generations in flowering plants

II.Evolutionary Themes in Plants-plants developed from filamentous green algae-trend toward a completely terrestrial existence

1. rely less and less on water for reproduction2. mechanisms to control water loss3. vascular tissues for transport

a. xylem: transport of waterb. phloem: transport of food (sugars)

--lightweight, resilient spores that can go dormant

-protective packaging for gametes and embryos -prolonged sporophyte and reduced gametophyte

generation

Fig. 23.4 Reduction in the size of the gametophyte

Angiosperms – Flowering Plants

A. reproductive structures are flowersB. largest and most diverse group of plants on earthC. divided into two broad classes:

1. monocotyledonae (monocots)• most herbaceous plants, grasses,

weeds, agricultural plants

2. eudicotyledonae (eudicots)• all woody plants, some herbaceous

plants