Size and surface area

• What is the main factor that affects the exchange of substances in organisms?

  Surface area to volume ratio
• Why do cells need to exchange substances with their environment?

  To take in oxygen and nutrients and to excrete waste products
• What are two waste products that cells need to excrete?

  Carbon dioxide and urea
• How does the surface area to volume ratio affect smaller animals compared to larger animals?

  Smaller animals have a higher surface area to volume ratio
• If a hippo is represented as a cube measuring 4 cm x 4 cm x 2 cm, what is its volume?

  $32 \text{ cm}^3$
• What is the surface area of a cube hippo measuring 4 cm x 4 cm x 2 cm?

  $64 \text{ cm}^2$
• What is the surface area to volume ratio of the cube hippo?

  1. 1
• If a mouse is represented as a cube measuring 1 cm x 1 cm x 1 cm, what is its surface area?

  $6 \text{ cm}^2$
• What is the surface area to volume ratio of the cube mouse?

  1. 1
• Why do multicellular organisms need specialized exchange organs?

  To efficiently supply every cell with substances and remove waste products
• Why is diffusion too slow for multicellular animals?


  Because some cells are deep within the body and there is a large distance to cover
• What system do multicellular organisms use for mass transport?

  The circulatory system
• What substances does the circulatory system transport in mammals?

  Glucose, oxygen, hormones, antibodies, and waste products
• What are the two main transport systems in plants?

  Xylem and phloem
• How does body size and shape affect heat exchange in organisms?

  Heat loss depends on surface area; larger volume with smaller surface area makes heat loss harder
• Why do smaller organisms need a relatively high metabolic rate?

  To generate enough heat to stay warm due to higher heat loss
• How does body shape influence heat loss in animals?

  Compact shapes minimize heat loss, while elongated shapes increase it
• What adaptations do small desert mammals have to reduce water loss?

  Kidney structures that produce less urine
• What behavioral adaptation do hippos use to keep cool?

  Spending much of the day in water
• What are the four things that organisms need to exchange with their environment?

  • Oxygen
  • Nutrients
  • Waste products (like carbon dioxide and urea)
  • Heat
• How does body shape affect heat exchange in animals?

  • Compact shapes minimize heat loss
  • Elongated shapes increase heat loss
  • Adaptations vary based on environmental temperature
• What adaptations do organisms have to aid in exchange and mass transport?

  • Specialized exchange organs (e.g., lungs)
  • Efficient mass transport systems (e.g., circulatory system)
  • Behavioral adaptations (e.g., spending time in water)
  • Physiological adaptations (e.g., kidney structures)
• How do smaller mammals adapt to cold environments?

  • Eat large amounts of high-energy food
  • Develop thick layers of fat
  • Hibernate during extreme cold