Characteristics of Living Things

Key Characteristics

1. Made of Cells

   • Basic unit of life.
   • Types:
     • Unicellular: Single cell organisms (e.g., Amoeba).
     • Multicellular: Multiple cells (e.g., humans).

2. Use Energy (Metabolism)

   • Requires energy for growth, repair, and maintenance.
   • Processes:
     • Photosynthesis: Converts sunlight to chemical energy in plants.
     • Cellular Respiration: Converts glucose to ATP in plants and animals.

3. Respond to Stimuli

   • Detect and respond to environmental changes.
   • Examples: Blinking, pulling away from heat, coughing.

4. Maintain Homeostasis

   • Regulation of stable internal conditions.
   • Examples: Sweating, shivering, regulating blood sugar.

5. Grow and Develop

   • Growth: Increase in size and mass.
   • Development: Progression through life stages.
   • Examples: Caterpillar to butterfly, humans growing.

6. Reproduce

   • Biological process to produce new organisms.
   • Types:
     • Asexual: Single parent, genetically identical offspring.
       • Methods: Budding, fragmentation, binary fission, spore formation.
     • Sexual: Two parents, genetic variation in offspring.

7. Contain Genetic Material

   • DNA/RNA necessary for growth, development, reproduction.

8. Adaptation

   • Adjusting to environmental changes to survive.
   • Animal Examples:
     • Behavioral: Bears hibernate.
     • Structural: Rabbits have big ears.
     • Physiological: Snakes produce venom.
   • Plant Adaptations:
     • Deserts, tropical rainforests, temperate forests, water environments.

Parts of a Flower Involved in Reproduction

1. Stamen (Male part)

   • Anther: Produces pollen grains.
   • Filament: Supports the anther.

2. Carpel (Pistil) (Female part)

   • Stigma: Catches pollen.
   • Style: Connects stigma to ovary.
   • Ovary: Contains ovules.

Steps in Sexual Reproduction

1. Pollination
   • Transfer of pollen from anther to stigma by wind, insects, etc.
2. Fertilization
   • Pollen tube grows to ovary, male gamete fuses with female gamete.
3. Seed and Fruit Formation
   • Zygote forms embryo, ovule becomes seed, ovary becomes fruit.

Cell Structure and Function

Plant Cell Organelles

• Cell Wall: Structural support, protection.
• Cell Membrane: Regulates movement in/out.
• Nucleus: Contains DNA, controls activities.
• Chloroplasts: Photosynthesis site.
• Vacuole: Stores nutrients and waste.
• Mitochondria: Energy production.
• Endoplasmic Reticulum: Protein and lipid synthesis.
• Golgi Apparatus: Modifies, sorts, packages proteins/lipids.

Animal Cell Organelles

• Similar to plant cells minus chloroplasts and cell wall.
• Lysosomes: Break down waste.
• Centrioles: Involved in cell division.

Necessities of Life

• Air/Gases: Oxygen for animals, carbon dioxide for plants.
• Source of Energy: Autotrophs (e.g., plants), heterotrophs (e.g., animals).
• Space: Required for growth, reproduction, resource access.

Specialized Cells and Adaptations

Animals

• Red Blood Cells: Oxygen transport.
• Nerve Cells: Signal transmission.
• Muscle Cells: Movement.

Plants

• Root Hair Cells: Absorb water/nutrients.
• Guard Cells: Regulate gas exchange.
• Xylem Cells: Transport water.

Key Terms

• Unicellular/Multicellular: Number of cells.
• Prokaryotic/Eukaryotic: Presence of nucleus.
• Homeostasis: Stable internal environment.
• Reproduction: Asexual vs. sexual.
• Stimuli: Environmental changes eliciting responses.

Practice Questions

1. List characteristics of living things with examples.
2. Compare plant and animal cells.
3. Function of mitochondria and its importance.