Edited Invalid date
14.1 The Plant Kingdom
There is a diversity of plants including oils and dates.
Human and animal populations are fed wheat.
The cotton flower's fibers are turned into clothing or paper.
The showy opium poppy is a source of potent opiate compounds and is valued both as an ornamental flower and as a source of potent opiate compounds.
All plants are descendants of a single common ancestor according to current evolutionary thought.
The ancestors of modern plants were constrained by the transition from water to land.
To avoid drying out, plants had to evolve strategies, such as dispersal of reproductive cells in air, for structural support, and to filter sunlight.
Full independence from water was not achieved in all plants, and most seedless plants still need a moist environment.
Plants are a diverse group of organisms.
There are hundreds of thousands of plants.
There are 260,000 plants that produce seeds.
The plant kingdom includes mosses, ferns, conifers, and flowering plants.
The plant kingdom has mostly photosynthetic organisms, but a few have lost the ability to photosynthesize.
The process of photosynthesis uses a plant.
Plants have cell walls.
Plants have different methods of reproduction.
Plants grow body mass until they die, meaning they don't have a final body form.
As organisms adapt to life on land, they have to contend with a number of challenges.
The majority of the chemical reactions of metabolism take place in the cell's interior, which is a watery soup.
Desiccation is a constant danger for organisms exposed to air.
When parts of a plant are close to water, their aerial structures are likely to dry out.
Water helps organisms live in aquatic habitats.
Plants need structural support in air, a medium that does not give the same lift.
Swimming is no longer possible for the male and female gametes.
Gametes and zygotes need to be protected from drying out.
The successful land plants adapted to all of the challenges.
Some species left the water and went on to conquer the driest environments on Earth, while others didn't move far from an aquatic environment.
Life on land offers a number of advantages.
Sun is abundant.
The water in the water column above does not affect the quality of light absorbed by the photosynthetic pigment, chlorophyll.
The concentration of carbon dioxide in air is higher than in water.
Until dry land was colonized by animals, there was no threat to the well-being of plants.
The situation changed when animals emerged from the water with abundant sources of food and water.
Plants evolved strategies to deter predator: from thorns to toxic chemicals.
Like the early land animals, the early land plants developed survival strategies to combat the effects of dry weather.
One of the strategies is tolerance for dry weather.
Mosses can dry out to a brown and brittle mat, but as soon as rain makes water available, mosses will soak it up and regain their green appearance.
It is possible to colonize environments with high humidity.
Ferns thrive in damp and cool places, such as the understory of temperate forests.
Plants used resistance to desiccation rather than tolerance to move away from aquatic environments.
These plants are able to survive in the driest environments on Earth because of their low water loss.
Land plants have adapted to life on land and this has an effect on their diversity and predominance in the land.
Alteration of 1 is one of the major adaptations found in many plants.
A sporangium, a gametangium that produces haploid cells, and apical meristem tissue can be found in this OpenStax book.
Alternation of generations is a description of a life cycle in which both haploid and diploid multicellular stages are present.
Humans are diplontic.
It can be the most obvious phase of the life cycle of the plant, as in the mosses, or it can occur in a tiny structure, such as a pollen grain in the higher plants.
The collective term for the plant groups of mosses, liverworts, and hornworts is the sporophyte stage.
Sequoias and pines have towering trees in their lifecycles.
The term "spore in a vessel" refers to a reproductive sac that contains spores.
The sporangia releases the spores in the environment.
The sexes are separated at different points in the life cycle when two different types of spores are produced in land plants.
The male and female gametophytes are called microspores because of their smaller size.
In a few seedless plants and in all seed plants, Heterospory is observed.
The haploid spore creates a multicellular gametophyte.
The life cycle of a fern shows a variety of generations.
The life cycle of a moss shows a variety of generations.
The thick cell walls that surround the seeds of seedless plants and the pollen of seed plants are made of a tough substance known as sporopollenin.
The yellow color of most pollen is due to the long chains of organic molecules in this substance.
It is resistant to chemical and biological degradation.
The existence of well-preserved fossils of pollen is explained by its toughness.
Land plants need protection of the embryo.
The embryo needs to be protected from desiccation.
In both seedless and seed plants, the female gametophyte provides nutrition and the embryo is protected as it develops into the new generation of sporophyte.
Gametangia are structures on the gametophytes of seedless plants in which gametes are produced.
The male gametangium releases sperm.
Many seedless plants have flagella that allow them to swim in a moist environment to the female gametangium.
The embryo is inside the archegonium.
The apical meristem is a cap of cells at the shoot tip or root tip made of undifferentiated cells.
All the specialized tissues of the plant are created by meristematic cells.
Light and water can be found in the shoots and roots, as well as minerals, which can be found in the roots.
Cells that increase the diameter of stems and tree trunks are produced by a separate meristem.
Apical meristems allow plants to grow in ways essential to their survival: upward to greater availability of sunlight, and downward into the soil to obtain water and essential minerals.
An example of a plant in which the apical meristem gives rise to new shoots and root growth is the apple seedling.
New organs and structures appeared as plants became independent of the constant presence of water.
Early land plants did not grow above a few inches off the ground, and they competed for light on these low mats.
Individual plants captured more light by growing taller.
Land plants incorporated more rigid molecules in their stems because air offers less support than water.
Plants had to evolve larger bodies in order to distribute water and solutes.
The xylem and phloem tissues are in the vascular system.
Xylem takes water and minerals from the soil up to the shoot and phloem takes food from the plant.
The shoot in the soil was anchored by the root system that took up water and minerals.
The leaves and stems of a land plant are covered with a waterproof cover called a cuticle.
The intake of carbon dioxide is prevented by the cuticle.
Plants that moved into drier habitats had open and close to regulate traffic of gases and water.
Plants can't avoid predatory animals.
They synthesise a large range of poisonous secondary metabolites, such as alkaloids, whose unpleasant smells and taste deter animals.
These compounds can cause diseases and even death.
As plants coevolved with animals, sweet and nutritious metabolites were developed to lure animals into providing valuable assistance in dispersal of pollen grains, fruit, or seeds.
Plants have evolved with animals.
Plants have adapted to life on land.
fundamental questions of evolution include how organisms acquired traits that allow them to colonize new environments and how the modern environment is shaped.
Paleobotany focuses on the study of extinct plants.
Paleobotanists reconstituting the morphology of organisms that have long disappeared by analyzing specimen retrieved from field studies.
They trace the evolution of plants by following the modifications in plant morphology and by identifying common ancestors that display the same traits.
There are gaps in the path to the development of modern organisms.
Fossils are formed when organisms are trapped in environments where their shapes are preserved.
The age of the fossils and the nature of the environment are determined by paleobotanists.
The delicate fossils and the layers in which they are found require great care.
The use of analytical chemistry and molecular biology to study fossils is one of the most exciting recent developments in paleobotany.
The environment free of oxygen is needed for the preservation of molecular structures since oxidation and degradation of material depends on the presence of oxygen.
Oleanane, a compound that deters pests and appears to be unique to flowering plants, is an example of analytical chemistry and molecular biology being used.
The current dates for the appearance of the first flowering plants are incorrect because Oleanane was recovered earlier.
The most information comes from fossils of nucleic acids.
They are compared to living organisms.
Evolutionary relationships can be built through this analysis.
Some paleobotanists don't agree with the conclusions drawn from the analysis of fossils.
The chemical materials of interest degrade quickly when exposed to air and further manipulation.
There is a high chance that the specimen will be contaminated with extraneous material.
As technology is refined, the analysis of DNA from plants will provide valuable information on the evolution of plants and their adaptation to an ever-changing environment.
Early in land plant evolution, the bryophytes, liverworts, mosses, and hornworts are seedless and nonvascular.
The lycophytes, which include club mosses, and the pterophytes, which include horsetails, are similar to the first vascular plants.
Plants that are seedless are referred to as lycophytes.
They don't produce seeds because they don't have enough food to make them.
The seed plants form the largest group of plants and dominate the landscape.
Review flashcards and saved quizzes
Getting your flashcards
Privacy & Terms