Introduction to Plants
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Transcript of Introduction to Plants
Key ConceptsWhat characteristics do all plants share?What do plants need to live successfully on
land?How do nonvascular plants and vascular
plants differ?What are the different stages of a plant’s life
cycle?
Key Termsphotosynthesis
tissuechloroplast
vacuolecuticle
vascular tissuefertilization
zygotenonvascular plant
vascular plantchlorophyllsporophyte
gametophyte
What Is a Plant?Members of the plant kingdom share several
characteristics.1. Nearly all plants are autotrophs, organisms that
produce their own food.2. All plants are eukaryotes that contain many cells.3. All plant cells are surrounded by cell walls.
Plants are AutotrophsThe textbook refers to a typical plant as a sun-powered, food-making factory. What provides
the energy for this food-making process?photosynthesis
During photosynthesis, a plant uses carbon dioxide gas and water to make food and
oxygen. We will look at this process more closely in section 2.
Plants Are MulticellularEukaryotes are organisms that contain many
cells.No matter how large or small a plant is, its
cells are organized into tissues-groups of similar cells that perform a specific function in an organism.
An example would be the vascular tissue that transports materials throughout the plant’s body.
Plant CellsUnlike the cells of some other eukaryotes, a plant’s
cells are enclosed by a cell wall.The cell wall surrounds the cell membrane and
separates the cell from the environment.Plant cell walls contain cellulose, a material that
makes the walls rigid. Cell walls are what make apples and carrots crunchy.
Plant cells contain structures called chloroplast-where food for the plant is made.
Plant cells also contain a vacuole or large storage sac that stores many substances, including water, wastes, and food.
Reading CheckpointWhat is the function of the vacuole in a plant
cell?The function of a vacuole in a plant cell is to store substances including water, wastes, and
food.
Adaptations for Living on landFor plants to survive on land, they must:
1. Have ways to obtain water and other nutrients from their surroundings (obtaining water and nutrients from the soil through roots)
2. Retain water (cuticle-waxy, water proof layer that helps a plant reduce water loss)
3. Transport materials in their bodies (vascular tissue-system of tubelike structures inside a plant through which water, minerals, and food are transported)
4. Support their bodies (Rigid cell walls and vascular tissue strengthen and support the bodies of large plants)
5. Reproduce (Fertilization, when a sperm cell unites with an egg cell, occurs resulting in a zygote-the fertilized egg)
Reading CheckpointWhy do plants need adaptations to prevent
water loss?Plants must have ways of holding onto the
water they obtain, otherwise they could easily dry out due to evaporation.
Classification of PlantsPlants are grouped into two major groups-
nonvascular plants and vascular plants.o Nonvascular plants are plants that lack a well-
developed system of tubes for transporting water and other materials.
o Vascular plants are plants with true vascular tissue.
Nonvascular PlantsNonvascular plants do not have true vascular
tissue for support or transport. They grow low to the ground.
They obtain water and materials directly from their surroundings.
The materials then pass from one cell to the next.This slow method of transport helps explain why
most nonvascular plants live in damp, shady places.
Most vascular plants have only thin cell walls to provide support.
Three Major Groups of Nonvascular PlantsMosses-Grow in damp, shady placesLiverworts-Often found growing on moist soil
and rocksHornworts-Usually grow on moist soil, often
mixed with grass plants
Vascular PlantsVascular plants are better suited to life in dry
areas than are nonvascular plants.Their well-developed vascular tissue solves
the problem of transport, moving materials quickly and efficiently throughout the plant’s body.
Vascular tissue also provides strength, stability, and support to a plant.
Vascular plants are able to grow quite tall.
Three Major Groups of Vascular PlantsSeedless Vascular Plants-Reproduce by
making sporesGymnosperms-Reproduce by seeds but do not
form flowers or fruitAngiosperms-Flower and produce seeds that
are surrounded by fruit
Origin of PlantsScientist have posed the question, “Which
organisms were the ancestors of today’s plants?”In search of an answer, biologist have studied the
fossils of ancient plants.Biologist compared the chemicals in modern
plants to those in other organisms.o In particular, biologist studied a green pigment called
chlorophyll, found in the chloroplasts of plants, algae, and some bacteria.
o It was found that land plants and green algae contain the same forms of chlorophyll.
o This evidence led biologist to infer that ancient green algae were the ancestors of today’s land plants.
Reading CheckpointWhat is chlorophyll?
Chlorophyll is a green pigment found in the chloroplast of plants, algae, and some
bacteria.
Complex Life Cycle of a PlantPlants have complex life cycles that include
two different stages, the sporophyte stage and the gametophyte stage.
In the sporophyte stage, the plant produces spores, tiny cells that can grow into new organisms. A spore develops into the plant’s other stage, called the gametophyte.
In the gametophyte stage, the plant produces two kinds of sex cells: sperm cells and egg cells.
Reading CheckpointDuring which stage does a plant produce
spores?A plant produces spores during the sporophyte
stage.