Exam 2 plants Flashcards
The Variety of Sexual Life Cycles
- Alternation of meiosis and fertilization is common to all sexually reproducing organisms
- Three main types of sexual life cycles differ in timing of meiosis and fertilization
A horse has 16 chromosomes in its gametes, how many does it have in its liver cell?
2n = 64
Animals (and Some Algae) Sexual Life Cycle -diagram 13.6a
n gametes via meiosis -fig
Plants (and Some Algae) Sexual Life Cycle
n gametes via mitosis
n spores via meiosis
Fungi (and Some Algae) Sexual Life Cycle 13.6c
n spores via meiosis
The Greening of Earth
Plants started getting taller to compete for light, 385 millions
ago
Archaeplastida
Supergroup includes red algae, green algae, land plants
- Descended from an ancient protist that engulfed a
cyanobacterium (i.e., endosymbiosis)
Land plants evolved from green algae
Green algae called charophytes are the closest relatives
of land plants
- Many characteristics of land plants also appear in a variety of protist clades, mainly algae
land plants share three key traits with only charophytes
– Rings of cellulose synthesizing proteins
– Structure of flagellated sperm – Formation of a phragmoplast
Adaptations Enabling the Move to Land
In charophytes a layer of a durable polymer called sporopollenin prevents exposed zygotes from drying out
- Sporopollenin is also found in plant spore walls
- Movement onto land by charophyte ancestors
provided unfiltered sun, more plentiful CO2, nutrient-rich soil, and few herbivores or pathogens
Derived Traits of Plants
Alternation of generations
– Multicellular, dependent embryos
– Walled spores produced in sporangia
– Multicellular gametangia
– Apical meristems
Note 1: some of these traits are lost in some lineages
* Note 2: some non-plant lineages also have some of
these traits (convergence)
Alternation of Generations
Plants alternate between two multicellular stages, a reproductive cycle called alternation of generations
- The gametophyte is haploid and produces haploid gametes by mitosis
- Fusion of gametes gives rise to the diploid sporophyte, which produces haploid spores
by meiosis
Exploring Derived Traits of Land Plants: Alteration of generations- figure 29.4-1
boom
Multicellular, Dependent Embryos
The diploid embryo is retained within the tissue of the female gametophyte
- Nutrients are transferred from parent to embryo through placental transfer cells
- Land plants are called embryophytes because
of embryo dependency on parent
Walled Spores Produced in -
sporangia
-the sporophyte produces spores in organs called sporangia
Diploid cells called sporocytes undergo meiosis to generate haploid spores
- Spore walls contain sporopollenin, which makes them resistant to harsh environments
Multicellular Gametangia
- Gametes are produced within organs called gametangia
- Female gametangia, called archegonia, produce eggs and are the site of fertilization
- Male gametangia, called antheridia, produce and release sperm
Apical Meristems
- Plants sustain continual growth in their apical meristems
- Cells from the apical meristems differentiate into
various tissues
Additional derived traits include:
The cuticle, a waxy covering of the epidermis
– Mycorrhizae, symbiotic associations between fungi and land plants
* may have helped plants without true roots to obtain
nutrients
What is in the phylum land plants?
all
-liverworts
-mosses
-hornworts
-lycophytes
-monilophytes
-gymnosperms
-angiosperms
what is in vascular plants?
the seedless vascular plants and seed plants
-lycophytes
-monilophytes
-gymnosperms
-angiosperms
What is in nonvascular plants
Liverworts
-mosses
-hornworts
What is in seedless vascular plants
Lycophytes
monilophytes
What is in group seed plants
gymnosperms
angiosperms
What phylum is in the nonvascular plants (bryophytes)
Phylum:
-hepatophyta
-bryophyta
-anthocerophyta