Gymnosperms

Gymnosperms are the oldest surviving seed plants. There are three classes, the Cycadae, Ginkgoae, and Confierae. Plants in these classes produce Scales. Scales are specialized male and female reproductive structures evolved from a number of leaves bunched together to form cones. Male cones produce pollen, male gametophytes. Female cones produce eggs, female gametophytes. During reproduction, the females cones hold the seeds that develop on their scales.


The name Gymnosperm, gymno meaning naked and sperm meaning seed, comes from the fact that their seeds sit "naked" on the scales.

                                                                     Cone

Here we have a cone that we observed in class. 

Here is a diagram of the reproduction of gymnosperms via alternation of generations. The process is similar to the life cycle of ferns, however gymnosperms spend even less time in the haploid stage. In the diagram above, after meiosis, the blue section is the haploid generation, and the pink section is the diploid generation.

There are many factors that contribute in helping gymnosperms survive in a land environment:

Roots:
Absorb water and nutrients from moist soil, anchor plants in the ground and prevent the wind and rain to knock the plants over from their upright position.

Stems:
Hold plant's leaves up so that they can absorb the sun's rays.

Leaves:
Are a plant's means of absorbing energy- essential for photosynthesis. Leaves also protect against water loss to dry air with their waxy coating called the cuticle.

Seeds:
Structures that protect the zygotes of seed plants. Contain plant embryos. A seed coat surrounds the embryos and makes sure that the food supply does not dry out. Seeds can survive harsh conditions, therefore it allows seed plants to survive and grow their population where mosses and ferns cannot. Once conditions are favorable again, the seeds begin to grow.

Pollen:
Pollen grains contain the entire male gametophyte of seed plants. Pollen grains are transported by wind, insects, and birds to female gametophytes in a process called pollination.

Vascular Tissue:
Makes up the two-way plumbing system found in plants. It consists of xylem and phloem, two different kinds of specialized vascular tissue.

• Xylem carries water and dissolved nutrients to leaves and stems from the roots. Xylem has thick cell walls, and strengthen wood parts of trees.

• Phloem transports the products of photosynthesis throughout the plant's body. Phloem cells carry their contents up and down. 

Ferns

Ferns, members of phylum Tracheophyta, are "true" land plants because their survival is not dependent on wet environments. Tracheophytes have specialized vascular tissues that transport water and the products of photosynthesis throughout the plant. Xylem, associated with the movement of water, and Phloem, responsible for transporting nutrients, are the two types of vascular tissue. 

Ferns have true vascular tissues, strong roots, underground stems called rhizomes, and Fronds, which are large leaves. Ferns are most abundant in moist, wet habitats.  
                       
                                      Preserved Fern Leaf

Here we have a picture through the lens of a microscope of a preserved fern leaf 

Here we have a general diagram of Alternation of Generation reproduction. It shows how haploid cells and diploid cells go through reproductive processes and combine to complete the life cycles of many land plants.

Here, more specifically, we have the life cycle of a Fern, which reproduces via alternation of generations. Ferns spend the majority of its life in Diploid form, the sporophyte generation, which we recognize as trees.

Ferns also have a special cell, Tracheid. These cells carry water from the roots underground to the leaves in the air. As you may have noticed, plants in phylum Tracheophyta are named after this unique cell. This is a feature that enabled Ferns to adapt to a land environment, much different to their algae ancestors living in marine environments.

Mosses

Phylum Bryophyta consists of mosses, liverworts and hornworts. Bryophytes have life cycles that involve an alternation of generations between a haploid gametophyte and a diploid sporophyte. Reproduction is dependent on water. Therefore, mosses can only survive in wet areas. Bryophytes do not have water conducting tubes, water passes from cell to cell by osmosis. They also lack a protective surface to keep water from evaporating from their cells. Also, mosses do not have true roots.


                                                 Moss 

Two different types of moss

                                           Sporophytes

Moss with very obvious sporophytes 

Moss Life Cycle

This is a diagram of the life cycle of a Moss. They reproduce via alternation of generations. They begin as spores, and develop into sex organs (haploids). The sex organs fertilize each other to form an embryo. This eventually produces a mature sporophyte (diploid). Then, once spores are released, the cycle begins once again. This process will be seen in most of the different types of life cycles we will be looking at.

http://www.sumanasinc.com/webcontent/animations/content/moss.html 
Above is a link to an awesome animation that explains the life cycle of a Moss more in detail.






Also, Moss have been able to adapt to a land environment because of their unique reproductive structures. The Antheridium and Archegonium, moss reproductive structures, protect games from drying out, giving the eggs of mosses a better chance at survival during dry, land conditions.

Algae

Algae are photosynthetic organisms that must live in or near a source of water. Unlike land plants, most algae lack an internal system. That means that they don't have tubes to transport water and materials from one part of the plant to another.Most algae are multicellular, however they can be unicellular, therefore, come in a great variety of sizes. The cells of algae have a cell wall.

Chlorophyta- Green Algae

Green algae are found in moist areas on land and in fresh water. Multicellular green algae contain cellulose in their cell walls, and store food in the form of starch, similar to land plants.

Green Algae Spirogyra
This is a picture through a microscope of a preserved specimen.

Ulva 

Ulva is a bright green multicellular marine alga also known as "sea lettuce." Ulva is found along rocky seacoasts. Ulva plants are only two cells thick.

Algae are food for most of oceanic life. They are known as the grasses of the seas. Algae also provides homes and habitats for marine animals. Life would not be the same without algae, because they produce a big part of Earth's free oxygen through photosynthesis. Algae is also used for human food products, all well as laboratory experiments. 

What is a plant? 

Kingdom Plantae includes multicellular, autotrophic organisms. Plants have a basic metabolism, the ability to sexually reproduce, the ability to respond to the environment, diversity and evolution just like other organisms in other kingdoms.However, plants are the primary producers in food webs and oxygenation of the atmosphere.

Plants are everywhere. They are not only beautiful to observe, plants replenish our supply of oxygen, which they give off during photosynthesis, and give off water, which lowers the temperature of the air. Plants are the food source of many other living things, and are what makes life on our planet possible for other organisms.