Transcript Angiosperms-the flowering plants have arrived

Angiosperms-the flowering
plants have arrived
Simone Neethling
Biodiversity and Conservation Biology
Department
University of the Western Cape
Available at http://planet.uwc.ac.za/nisl/Eco_people/Presentations/
Introduction



Angiosperms are flowering plants that
cover their seeds in a true fruit.
Their reproductive organs; an
androecium (male) and/or gynoecium
(female) lies within the flower structure.
Primitive angiosperms are dioecious
whereas modern angiosperms are
monoecious.
Angiosperms are highly successful and
dominate the vegetation of the earth’s
surface.
http://www.botanical-online.com/floresadaptacionesangles.htm

Classification
taken from Pearson(1995)
Morphology and anatomy





The androecium consists of stamens, made up of anthers and
filaments.
The gynoecium consists of the pistil, made up of the style and
stigma.
Pollen grains germinate on the stigma, grains have numerous
sutures through which a germination tube can emerge thereby
ensuring that grains will not land upside down and result in
unfavourable germination conditions.
The perianth, also forming part of the reproductive system,
consists of units that may be differentiated into petals and sepals.
There are two other organ systems in angiosperms as well as
other plants, namely an anchorage and production system.
Morphology and anatomy
http://www.botanical-online.com/floresadaptacionesangles.htm
Morphology and anatomy


Angiosperms are also anatomically complex
organisms.
Dicots have vascular tissues within their
stems, roots and leaves that is made up of
xylem and phloem bundles in a fixed
arrangement this arrangement distinguishes
dicots from monocots as monocots’ bundles
are scattered.
Dicots’ vascular bundles consist of
secondary xylem and phloem produced by
the cambium within.
http://www.botanical-online.com/floresadaptacionesangles.htm

Origin

http://www.botanicalonline.com/floresadaptacionesangleshtm

The Cretaceous era (145-65 million
years ago) saw the rise of flowering
plants and their associated insect
pollinators through the process of
co-evolution.
This process between plants and
insects was most probably the most
influential driving force behind the
origin and diversification of
angiosperms, although it has been
disputed that flexibility in seed
production, dispersal and seeding
establishment was the most
important factors in angiosperm
origin.
Origin





Two basic hypotheses:Magnolialean and Herbaceous origin
hypothesis.
The Magnolialean hypothesis suggests that the first angiosperms on
earth were woody with large, many parted flowers.
These flowering plants were shrubs of semi-xerophytic origin that
entered mesic areas as colonizers of unstable habitats – “the weeds
of the Early Cretaceous” based on fossil evidence.
These Magnolia – like ancestral angiosperms were distinguished
from cycad-like gymnosperms, from which they evolved, by having a
closed carpel, smaller leaves and sculptured pollen grains and loved
in disturbed habitats like stream margins and gravel bars with
coarse grained sediments.
Herbaceous origin hypothesis implies that the first Angiosperms
were small in size and had smaller, few parted flowers. This
hypothesis suggests that Angiosperms are derived from a
compound gymnosperm; similar to gnetopsids
Impact on other eco-systems


Angiosperms had major impacts on
the evolution of other types of
plants and animals.
The increase in angiosperms was
paralleled by the decline of ferns.
Another major driving force behind
the rise of angiosperms and
angiosperm fruit is the co-evolution
feedback between plants and
vertebrates that dispersed the fruit.
http://plantphys.info/Plants_Human/pollen.adapt.html

Angiosperm adaptations to pollination



Pollination is a process where pollen is transported from the anther
to the stigma.
Flowers have adapted in order to attract pollinators. Adaptations
include visual cues whereby colour patterns that resemble a “bull’s
eye” are utilized.
Pollinators therefore see the flower as the target and can be
differentiated from the background green foliage.
http://plantphys.info/Plants_Human/pollen.adapt.html
http://plantphys.info/Plants_Human/pollen.adapt.html
Angiosperm adaptations to pollination



Flowering plants have also adapted olfactory cues as some
pollinators use their olfactory sense much more than their visual
sense; some flowers are also not as visually stimulating as others
therefore flowers have also evolved scents.
During the process of pollination, pollinators need to benefit from
the transportation of pollen therefore rewards for the pollinator has
to be present. Flowers therefore produce nectar a valuable food
resource.
Flowers also produce extra pollen as some pollinators feed on
pollen e.g. bees.
http://www.botanical-online.com/floresadaptacionesangles.htm
Angiosperm adaptations to pollination

http://www.botanicalonline.com/floresadaptacionesangleshtm

The shape of the flower plays a
major role for example corollas of
some Erica’s are strongly curved
to match the beak shape of the
main pollinator, the Orangebreasted Sunbird found in South
Africa.
In fly-pollinated Erica’s, the mouth
of corolla is much smaller and
lobes are large, star-shaped and
spreading thereby providing a
landing pad for flies as they insert
their long proboscis into the
flower to drink nectar.
References

Corbet SA (1978) Bees and the nectar of Echium vulgare. Linnean
Society Symposium Series 6:21-30

Mader SS (2004) Biology 8th Edition. McGraw-Hill, New York, pp
428. ISBN 0-07-241882-6

Pearson LC (1995) The Diversity and Evolution of Plants. CRC
Press, Inc., United States of America, pp 524-529. ISBN 0-84932483-1

Taylor DW and Hickey LJ (1996) Flowering Plant Origin, Evolution
and Phylogeny. Chapman and Hall, New York, PP176-178. ISBN 0412-05341-
References





Angiosperms
http://en.wikipedia.org/wiki/Angiosperms#History
Accessed:13/03/2006
Angiosperms
http://www.geocites.com/we_evolve/plants/angiosperms.html
Accessed:13/03/2006
Pollination Adaptations
http://plantphys.info/Plants_Human/pollen.adapt.html
Accessed:28/03/2005
Flowers
http://www.botanical-online.com/floresadaptacionesangles.htm
Accessed:28/03/2005
http://www.unifiedworld.com
Accessed:28/03/2005