1. Plants!!!
7th Grade Science

2. What is a plant? Autotrophs Eukaryotes Plant Cells Photosynthesis
Use energy from the sun to make their food
Eukaryotes
Many cells organized into tissues
Tissues = groups of similar cells that performs a specific function
Plant Cells
Cell wall = boundary that surrounds the cell membrane and separates the cell from the environment
Cell walls made of cellulose, which makes them rigid
Chloroplasts
Vacuole = large storage area for water, food, wastes; expands and shrinks depending on how much water is in the cell

3. Where did plants come from?
Scientists study the fossil record for clues
Oldest plant fossils are about 400 million years old
Scientists study chlorophyll
Chlorophyll comes in different forms
Different forms have slightly different chemical structures
Plants and green algae have the same form of chlorophyll, so scientists infer that ancient green algae were the ancestor’s of today’s plants

4. How do plants survive on land?
Obtain/retain water and nutrients from their surroundings
Plants have adaptations that allow them to get water and nutrients from the soil
Plants have adaptations to stop the water in their cells from evaporating into the air
Common adaptation is the cuticle, a waxy, waterproof layer that covers the plant’s leaves
Transport materials throughout the plant
Food made in the top part of a plant, water absorbed through the bottom part, plant has to have vascular tissue which can move food and water throughout the plant
Reproduce
All plants undergo sexual reproduction
Fertilization occurs when a sperm cell unites with an egg cell
Fertilized egg = zygote

5. Plants have a complex life cycle!
Two different stages/generations
Stage 1 = Sporophyte
Plant produces spores
Spores are tiny cells that can grow into new organisms
Spores develop into stage 2
Stage 2 = Gametophyte
Plant produces two kinds of sex cells
Gametes (sex cells) are sperm cells and egg cells
P. 307

6. Plant Life Cycle Sperm cell and egg cell join to form the zygote
Zygote develops into a sporophyte
Sporophyte produces spores
Spores develop into gametophyte
Gametophyte produces sperm and egg cells

7. Nonvascular Plants
Nonvascular plants are plants that are low-growing and lack vascular tissue
Examples of nonvascular plants include mosses, liverworts, and hornworts
Remember that vascular tissue transports water and nutrients throughout a plant, so nonvascular plants don’t have this
Nonvascular plants are only able to transport material from one cell to a cell directly next to it, so materials do not travel far or quickly
These plants obtain water and nutrients from their surroundings directly
Need to have enough water nearby so that sperm cells can swim to the egg cells during reproduction

8. Mosses Over 10,000 species of moss, can grow in many places
Picture p. 316
Moss that we think of is the gametophyte generation
Rhizoids = thin, root-like structures that anchor the moss and absorb water and nutrients
Sporophyte generation grows out of the gametophyte, consists of a slender stalk with a capsule at the end, capsule has spores

9. Moss!

10. Liverworts and Hornworts
8,000 species of liverworts
Liverworts named for the shape of the plant, which looks like a human liver
Liverworts grow flat along the ground, in moist soil or near streams
Fewer than 100 species of hornworts
Slender, curved structures grow out of the gametophytes – this is the sporophyte, which looks like a horn
Hornworts live in moist soil

11. Liverworts and Hornworts

12. Seedless Vascular Plants
This category includes ferns, club mosses, and horsetails
Two characteristics in common – vascular tissue and the use of spores in reproduction
Vascular tissue allows these plants to transport nutrients and water
Vascular tissue also strengthens and stabilizes the plant’s body
Grow in moist surroundings, where spores can grow into gametophytes and there is enough water available for fertilization to occur

13. Ferns 12,000 species of ferns Ferns have true roots, stems, and leaves
Stems are underground, leaves grow upward from sides of the stem, roots grow downward from stem
Roots anchor the fern to the ground and absorb water and nutrients
Fronds = fern’s leaves, fronds are divided into many smaller parts
Upper surface of each frond has a cuticle
Developing fronds curl at first, called fiddleheads, uncurl as the frond develops

14. Ferns

15. Ferns Fern that is familiar to us is the sporophyte generation
Spores develop on the underside of fronds
Wind and water can carry spores great distances
If a spore ends up in favorable conditions, it will grow into a gametophyte

16. Club Mosses Club mosses are small
Not a true moss, club mosses have vascular tissue
Ground pine/princess pine are examples of club mosses
Grow in moist woodlands and near streams

17. Horsetails Only 30 species today Stems of horsetails are jointed
Long, coarse, needle-like branches grow in a circle around each joint
Small leaves grow flat against the stem just above each joint

18. Seed Plants Seed plants outnumber seedless plants more than 10 to 1
Seed plants share two characteristics
Vascular tissue
Xylem = vascular tissue that moves water from roots upward
Phloem = vascular tissue that moves food from leaves downward
Use seeds to reproduce
Sporophyte generation = the plant we see, the gametophytes are microscopic

19. Seeds
Seeds = structures that contain a young plant inside a protective covering
Seed plants do not need water to reproduce
After sperm cells fertilize the eggs, seeds develop
All seeds have three parts
Embryo = fertilized egg, develops from the zygote, has the beginnings of roots, stems, and leaves
Stored food = uses this food until it’s big enough to make it’s own food, cotyledon
Seed coat = protects embryo and food from drying out

20. Seeds

21. Seed Dispersal Seeds need light, water, and nutrients
Seeds will sprout when they land in a suitable area
Seeds are dispersed in many ways
Animals
Travel through digestive track and then are deposited
Travel by hooking onto fur/clothes
Water
Seeds float along until deposited (remember deposition?)
Wind
Wind disperses lightweight seeds

22. Seed Dispersal

23. Germination Germination = early growth stage of the embryo
Begins when seed absorbs water from environment, embryo uses stored food
Roots grow downward, then leaves and stems grow upward
Seeds dispersed far from parents have a better chance for survival because they’re not competing for resources

24. Germination

25. Leaves Most numerous part of plants, wide variety of shapes and sizes
Leaves capture the sun’s energy and carry out photosynthesis (chloroplasts)
P. 335 (Structure of a Leaf)
Top and bottom layers of the leaf protect the cells in between
Xylem and phloem are in the center of the leaf
Stomata (carbon dioxide/oxygen gas exchange)
Transpiration = the process by which water evaporates through the leaves

26. Leaves

27. Stems
Stem has two functions – (1) carries substances between the roots and the leaves and (2) provides support for the plant and holds leaves up so they are exposed to the sun
Wide variety of shapes and sizes (some are underground or very small, others are most of the plant!)
Herbaceous vs. woody stems
Woody stems have bark
Annual rings (xylem)

28. Roots
Roots = anchor a plant in the ground, absorb water and nutrients from the soil
Taproot vs. fibrous roots
P. 338
Taproot = one thick, long main root
Fibrous roots = several main roots that branch off and form a mass of roots
Root structure
Root cap = contains dead cells, protects root from injury as it grows through the soil
Root hairs = increase surface area to better absorb water/nutrients

29. Roots
Taproot
Fibrous Roots

30. Gymnosperms
Gymnosperms = produce naked seeds (meaning their seeds have no protective covering)
Many gymnosperms have needlelike leaves and deep-growing root systems
4 groups of gymnosperms
Cycads
Ginkgo
Gnetophytes
Conifers

31. Gymnosperms
Cycad, ginkgo, and gnetophyte

32. Conifers Conifers = cone-bearing plants
Pines, redwoods, cedars, hemlocks, junipers
Evergreen plants = keep their leaves (needles) year-round

33. Gymnosperm Reproduction
A single plant produces both male and female cones
Male cones produce pollen, pollen contains microscopic cells that will develop into sperm
Female cones contain an ovule, which contains an egg cell
After fertilization, ovule develops into a seed
p. 344
Pollen falls from a male cone onto a female cone, sperm cell joins with the egg cell in an ovule, fertilization occurs, zygote develops into the embryo part of the seed.
Pollination = transfer of pollen from the male to the female reproductive structure.

34. Angiosperms
Angiosperm = plant that produces seeds that are enclosed in a fruit, produce flowers and fruits
Ovary = protected part of the plant where seeds develop, located within the flower
Flower = reproductive structure of angiosperms
p. 347 (structure of a flower)
Petals and sepals
Stamens = male reproductive part (anther, filament)
Pistils = female reproductive part (stigma, style, ovary)

35. Parts of a Flower

36. Angiosperm Reproduction
Pollen falls on stigma, sperm and egg cell join together in the ovule, zygote develops into the embryo part of seed
Flower is pollinated when pollen falls on stigma, most pollination occurs by animals
Ovary changes into a fruit – this is how seed dispersal occurs

37. Types of Angiosperms Monocots Dicots One seed leaf
Grasses, corn, wheat, rice, lilies, tulips
Either three petals or a multiple of three petals
Long, slender leaves
Two seed leaves
Roses, violets, dandelions, oak trees, maple trees, beans, apples
Flowers have four or five petals or multiples of four or five petals
Leaves are wide

38. Plant Responses
Tropism = plant’s growth response toward (positive tropism) or away (negative tropism) from a stimulus
Touch = Thigmotropism
Coiling vines
Light = Phototropism
Leaves, stems, and flowers grow toward light
Gravity = Gravitropism
Roots show positive gravitropism, they grow toward the pull of gravity
So what about stems?

39. Plant Hormones
Hormone = chemical that affects how the plant grows and develops
Plant hormones control germination, the formation of flowers, stems, leaves, shedding of leaves, developing and ripening of fruit

40. Plant Review!
All plants are autotrophic, eukaryotic, and multicellular
All plants have a sporophyte and gametophyte generation
Plants need the same things that ALL living things need!
Photosynthesis (where does it occur? what is the formula?)
Nonvascular, seedless vascular, and seed plants (gymnosperms and angiosperms)
Plant responses = tropisms