Biodiversity – Oct. 1/12
- The Archaeplastida branch of the tree consists of the following groups, and they are all monophyletic
except for green algae, which are paraphyletic: rhodophyta (red algae), green algae, embryophyta
(land plants), bryophyte (moses), lycopodiopsida (lycophytes), polypodiopsida (ferns and
horsetails), spermatopsida (seed plants), conifers (cone-bearing seed plants), angiosperms (seed
plants that also have flowers).
- Angiosperms are the most diverse group of land plants and they comprise 2/3 of earth’s plants.
Angiosperms also contain fruits with seeds. Most flowering plants are eudicot and some are
- Modes of reproduction: Asexual reproduction – Offspring arise from a single parent, without meiosis
and fertilization. Offspring are an exact genetic copy of the parent. This occurs in archaea, eubacteria,
and single-celled eukaryotes. It sometimes occurs in plants and fungi and it rarely occurs in animals.
Sexual reproduction – This is the primary method of reproduction for the vast majority of
macroscopic life. Meiosis is the production of haploid gametes with half the number of chromosomes.
Fertilization is the fusion of two gametes from different individuals, eventually producing an embryo
containing the original number of chromosomes. It results in increased genetic diversity within a
species, allowing for adaptation to changing environments. Many plants are capable of both sexual
and asexual reproduction (ex. vegetative reproduction).
- Pollination: In seeds plants, pollination is the transfer of pollen from the male plant parts to the
female parts, followed by fertilization. Pollen is a fine/course powder made up of grains which
contain the male gametes. Cross-pollination involves two individuals. Self-pollination is when a
flower or plant is pollinating itself, but this doesn’t happen often because most plants are unable to
- Conifers are seed plants and they undergo sexual reproduction. The male cones produce pollen and
the wind carries the pollen to the female cones, which generate seeds.
- Angiosperms (flowering plants): Flowers provide nectar and pollen that attract animals. While the
animal is eating or gathering food, it pollinates the flower, usually by accident.
- In flowers, the reproductive parts stick out and flowers have both male and female parts. The pollen
produced by the male parts lands on the female parts of a different plant. Some fruits that contain
seeds include strawberries and beans.
- Seed plant life cycle – sexual reproduction in angiosperms: The entire plant is the flower. It contains
petal and septals, which are smaller green parts coming off the stem. The stamen is the male part,
and it consists of a filament and the anther, which is the small bulb thing that releases the pollen. The
female parts are the style and the stigma, which is the tip part that receives the pollen. Once the
stigma receives the pollen/sperm, it travels down into the ovary where it fertilizes with egg. The
ovary develops into a fruit with seeds. Nectar is a sugar-rich liquid that attracts animals. It is at the
base of the flower. Animals get pollen on their bodies while getting nectar, and they accidently
transfer the pollen to other plants.
- Pollination – co-evolution between plants and animals: Pollen is transferred from one plant to
another, enabling cross-fertilization, and in some cases, self—fertilization. 20% of pollination occurs
via abiotic things – wind, conifers, grasses, flowering trees, water. 80% of pollination occurs via biotic
things – insects (bees, wasps, ants, beetles, moths, butterflies, flies), bats, birds. Most pollinators are
- Example – A butterfly is sitting on a daisy flower. It has a sucking tube that is sucking up nectar from
the flower. While it’s doing this, pollen is getting stuck to its body. It will transfer this pollen to
another flower if it flies to another one. This will result in pollination and fertilization of this flower.