LAS PLANTAS 1º ESO

Introduction to the Fascinating World of Plants

Overview of Plant Characteristics

• The session introduces plants as multicellular eukaryotic organisms composed of plant cells, highlighting their autotrophic nutrition shared with algae and some bacteria.

• Key features include cell organelles like mitochondria and Golgi apparatus, a cellulose cell wall, and chloroplasts containing chlorophyll for photosynthesis.

Plant Structure and Tissue Types

• Plants are multicellular organisms organized into various tissues with distinct functions; four main tissue types are identified:

• Chlorophyllous parenchyma (photosynthesis/storage)

• Supportive meristems (growth/structure)

• Protective epidermal tissues (external protection)

• Conductive tissues (transportation of sap).

Plant Organs Overview

Introduction to Plant Organs

• The main organs of spermatophyte plants include roots, stems, leaves, flowers, and seeds.

Roots

• Roots typically grow underground opposite to the stem and are white due to a lack of chlorophyll. They anchor the plant in soil and absorb water and minerals.

• Roots have a branched structure with a primary root and secondary roots; they feature fine absorbent hairs at their tips. The growth zone is protected by a cap.

• Types of roots include:

• Articulated roots: Lack a main axis.

• Tuberous roots: Serve as storage organs.

• Axon or more fast roots: Have a prominent main root with deep-growing secondary roots.

Stems

• Stems are aerial organs that grow opposite to the roots, conducting raw sap and elaborated sap within the plant system while supporting leaves.

• Stems contain nodes (junction points between stem and branches) and internodes (spaces between two nodes). Axillary buds promote leaf, flower, and branch growth; terminal buds contribute to lengthening the plant.

• Stem types vary based on environment:

• Aerial, subterranean, or aquatic depending on their location.

• Consistency can be classified as herbaceous (green, soft) or woody (brown, hard).

• Growth habits include creeping (staying close to ground), climbing (ascending walls/trees), or succulent (thickened for storage).

• Lifespan classifications include annual (seasonal growth) or perennial (long-lasting).

Leaves

• Leaves are generally green due to chlorophyll; they grow from stems/branches and perform photosynthesis, gas exchange, and transpiration.

• Leaf structure includes:

• Petiole: Thin cylindrical part connecting leaf to stem.

• Lamina: Broad flat part of the leaf with two surfaces—one impermeable layer for protection against water loss containing stomata for gas exchange.

• Leaf types can be categorized by lamina number:

• Simple vs compound leaves.

• Various shapes such as circular or heart-shaped.

• Edges may be entire, serrated, lobed, etc., influencing classification further into pinnate or palmate venation patterns.

Flowers

• Flowers serve reproductive functions in angiosperms with diverse colors forming gametes for sexual reproduction; they consist of modified leaves including petals and sepals for protection.

• Flower anatomy includes:

• Peduncle: Connective stalk.

• Calyx: Protective green sepals.

• Corolla: Colored petals attracting pollinators.

• Male parts (Stamens) produce pollen grains containing male gametes; female parts (Pistil) house ovules for female gametes formation.

Flower Types

• Flowers can be complete (all parts present) or incomplete (missing one/more parts); they may also be hermaphroditic if both male/female structures exist or unisexual if only one type is present. Angiosperm flowers exhibit vast color diversity compared to gymnosperms which form cones without calyx/corolla structures but still facilitate sexual reproduction through organized inflorescences like pine cones where scales bear ovules/pollen grains respectively.

Seeds

• Seeds differ between gymnosperms and angiosperms in structure; visual aids illustrate seed components essential for understanding plant reproduction processes effectively.

Plant Reproduction and Structure

Seed Development in Gymnosperms and Angiosperms

• The green cotyledon serves as a nutrient store for the embryo, which is the yellow part of the radicle that will develop into roots, while the plumule develops into stems, leaves, and future flowers.

• In gymnosperms, seeds are typically pine nuts; after fertilization within the female inflorescence, the embryo develops inside what is called a pine nut.

• In angiosperms, seeds contain an embryo surrounded by protective structures known as fruits that may attract animals or facilitate dispersal through wind or water.

• The type of seed found in angiosperms varies based on fruit texture; examples include fleshy fruits like tomatoes and dry fruits like walnuts.

Characteristics of Ferns and Bryophytes

• Ferns are vascular plants without flowers or fruits; they were among the first to develop vascular systems on land. They reproduce alternately through sexual and asexual means.

• Bryophytes include mosses and liverworts; mosses have simple vascular structures but lack flowers or fruits. They absorb water directly from their environment due to their structure.

• Liverworts also lack vascular systems and reproduce alternately. They can only transport absorbed substances cell-to-cell via diffusion due to their structure.

Plant Life Cycle and Vital Functions

• All plant types share a life cycle: they are born, grow, reproduce annually, and eventually die. Throughout this cycle, they perform vital functions: nutrition, response to stimuli (relation), and reproduction.

Nutrition in Plants

• Photosynthesis is crucial for plants to obtain energy; it converts solar energy and inorganic matter into organic matter using water absorbed by roots.

• Carbon dioxide enters leaves through stomata during photosynthesis; raw sap travels from roots to leaves where it transforms into elaborated sap distributed throughout the plant.

Importance of Photosynthesis

• Chloroplast cells containing chlorophyll use light energy for converting inorganic materials into organic matter while releasing oxygen as waste through stomata during gas exchange.

Transpiration Process

• Transpiration helps move substances within plants by allowing excess water absorbed by roots to evaporate from leaves as vapor or tiny droplets.

Cellular Respiration in Plants

• Plants undergo cellular respiration using organic matter created during photosynthesis for energy needed in various processes throughout day and night cycles.

Plant Responses to Environment

Mechanisms of Response

• Plants respond to environmental stimuli through changes termed tropisms (growth responses towards stimuli).

• Nastias are temporary changes in plant form responding to external factors such as sunlight (e.g., sunflowers).

• Thigmonasty occurs when mechanical actions affect plants (e.g., carnivorous plants reacting to touch).

Understanding Plant Responses and Reproduction

Plant Responses to Stimuli

• Thermonasty vs. Tropisms: Thermonasty refers to temperature-induced responses, while tropisms are permanent changes in plant form due to stimuli. Phototropism occurs when plants grow towards light.

• Types of Tropisms:

• Gravitropism causes roots to grow downwards into the soil.

• Thigmotropism is observed when plants wrap around objects, such as fences.

• Hydrotropism involves growth towards water sources.

Reproductive Processes in Plants

• Sexual Reproduction: Begins with pollen production in flowers, which must be transported for pollination. The pollen travels to the stigma and forms a pollen tube containing male gametes.

• Fertilization Process: Fertilization occurs when the pollen tube reaches the ovule containing female gametes, leading to embryo formation within seeds that can germinate into new individuals.

Seed Dispersal Mechanisms

• Pollination Methods: Pollination can occur via wind (anemochory) or animals (zoochory), facilitating genetic diversity through seed dispersal mechanisms like wind, animal digestion, or water flotation.

• Asexual Reproduction Techniques: Plants can reproduce asexually using tubers (e.g., potatoes), bulbs (e.g., garlic), rhizomes (e.g., ginger), and stolons (e.g., strawberries). Cuttings from stems can also develop into new plants.

Importance of Plant Life Cycles

• Ferns and Their Dual Reproduction: Ferns exhibit both sexual and asexual reproduction phases. Spores produced by structures called sori lead to new individuals through asexual means.

• Mosses' Life Cycle: Mosses have distinct sexual and asexual phases; the gametophyte produces gametes that fertilize to form sporophytes, which release spores for further propagation.

Ecological Significance of Plants

• Oxygen Production & Carbon Absorption: Plants are crucial for producing oxygen and absorbing carbon dioxide, forming the base of food chains as primary producers while preventing soil erosion with their root systems.

• Water Cycle Participation: Through transpiration, plants move water from soil to atmosphere, contributing significantly to local humidity levels and overall ecosystem health.

Human Utilization of Plants

• Culinary & Industrial Uses: Humans have relied on plants for food (fruits/vegetables), industrial materials (cotton/lino), medicinal properties (valerian for calming effects), and ornamental purposes in homes.

The Importance of Dehesa for Agriculture and Livestock

Overview of Dehesa's Resources

• The dehesa is a vital ecosystem that provides numerous resources for both agriculture and livestock.

• It is known for producing high-quality products, such as Jamón de Jabugo, which comes from pigs that thrive in this environment.

• Pigs raised in the dehesa benefit from a diet rich in acorns, which contributes to the flavor and quality of the meat.

• The ability of pigs to roam freely in these areas enhances their health and well-being, making them more suitable for premium meat production.

• The discussion highlights the ecological significance of dehesas in supporting sustainable agricultural practices.