PSC102 Lecture Notes - Lecture 1: Chlorophyll, Chickpea, Marchantiophyta
Botany (PSC-102)
Land plants: Organisms that are green and don’t move around (a simple definition)
Plants are defined as having the following characteristics:
1. They contain chlorophyll for absorbing light for photosynthesis (if nonphotosynthetic, they are
descended from photosynthetic ancestors).
2. They are adapted for life on land (e.g., have a multicellular embryo – embryophytes).
3. They have cell walls containing cellulose.
4. They are composed of many cells.
Five major Groups of Land plants:
Angiosperms – Flowering plants
Gymnosperms - Conifers
Pteridophytes - Ferns
Lycophytes – Liverworts & Hornworts
Bryophytes - Mosses
Evolution of angiosperm:
Angiosperms (flowering plants) are regarded as the most successful of land plants and are what we focus
on in this subject. (Estimated 352,000 species)
1. Vascular tissue: Vascular tissue = Xylem and phloem enabling support and conduction of water
& minteral (xylem) and sugars (phloem). Lignin in these tissues is tough and gives the support.
Enabled plants to get bigger/taller and transport water. Also roots replaced the rhizoids of
bryophytes (mosses, liverworts and hornworts)
2. Sporophyte dominant: What you need to know here is that plants have two parts of their life
cycle that alternate between each other and these are called the sporophyte generation and the
gametophyte generation. In bryophytes the gametophyte generation (only one set of
chromosomes -haploid) is dominant – takes up most of the life cycle. As plants evolved they went
from gametophyte being the dominant phase of the life cycle to the sporophyte (-two sets of
chromosomes – diploid) being dominant. In actual fact in ferns you can see the gametophyte –
size of your thumb but in gymnosperms and angiosperms it is much reduced to a few cells.
3. Seeds: Land plants up to an including ferns (pteridophytes) produce spores – you can see
masses of them on the underside of fern fronds. Seeds on the other hand are produced in
gymnosperms and angiosperms and are more likely to have genetic variability. They are also
tougher can lie dormant for a long time and contain food reserves.
4. Flowers/fruit: Flowers – especially brightly coloured ones – insect pollenation cross pollenation
from different members of the same species increases genetic variation. Fruits – dispersal of
seeds– fleshy eaten by animals. Others explosive seeds projected; parachutes wind dispersal
e.g. dandelion; burrs – animal fur transport; cats head
People and plants:
The fertile crescent in the near east is one of the key places Agriculture began.
Eight Neolithic founder crops (or primary domesticates) from Fertile Crescent- important in early
agriculture:
Cereals
1. Emmer (Triticum dicoccum, descended from the wild T. dicoccoides)
2. Einkorn (Triticum monococcum, descended from the wild T. boeoticum)
3. Barley (Hordeum vulgare/sativum, descended from the wild H. spontaneum)
Pulses
4.Lentil (Lens culinaris)
5.Pea (Pisum sativum)
6.Chickpea (Cicer arietinum)
7.Bitter vetch (Vicia ervilia)
Other
8. Flax (Linum usitatissimum)
Domestication: (from Latin domesticus: "of the home") is the process whereby a population of living
organisms is changed at the genetic level, through generations of selective breeding, to accentuate traits
that ultimately benefit the interests of humans.
Embryophytes:
