Unit 2: Cells and Systems

1. Unit 2: Cells and Systems

2. Topic 1: Living Organisms • Living organisms are found in all shapes and sizes, but have much in common. • Living organisms: • Need energy • Respond and adapt to their environment • Reproduce • Grow • Produce wastes

3. Functions and Structures 1. Energy • Animals get their energy from food • Plants get their energy from the Sun • What structures do plants and animals have to allow them to gather and use food for energy?

4. Functions and Structures 2. Environment - Plants move towards the Sun because they need light to make food - Animals find food at different times during the day (ex. raccoons and deer) 3. Reproduction - Do plants and animals reproduce in the same way? What structures enable plants and animals to reproduce?

5. Functions and Structures 4. Growth - What structures enable plants and animals to grow? - How do living organisms grow? 5. Wastes - Plants and animals release different waste products - Plants and animals have different structures in place to release wastes

6. Levels of Organization in Organisms • Organisms have specialized structures to carry out their various functions • Most organisms have systems that perform certain functions to keep the organism alive • Systems are made of organs • Ex. The heart is an organ of the circulatory system • Organs are made from tissues • System -> Organ -> Tissues • Fig. 2.1A-C

9. Levels of Organization in Organisms • The basic unit of every system is the cell • Cell: the smallest unit that can perform the functions of life • All living organisms are made up of cells • The cell is the smallest thing that scientists consider to be alive

10. Cells Work Together • The cells in a pika’s digestive system are organized into different tissues and organs that help the pika digest plants • The cells in our bodies are organized into tissues and organs that help us digest a variety of foods.

11. Topic 2: Microscopes and Cells • Microscopes help us to see things that are too small to see with the unaided eye • Magnify: to make objects appear larger by using a microscope or another magnifying instrument.

12. A World Too Small to See • The human eye can only see objects that are larger than 0.1mm • Separate dots must be more than 0.1mm apart in order for most people to see them as dots • Look at the circles of dots on page 103

13. Early Microscopes • Anton van Leeuwenhoek (1632-1723) • Microscope: an instrument that makes objects appear larger by bending light through a lens • His microscopes were able to magnify 300X • He studied blood, pond water, etc • Was the first to observe single-celled organisms which he called “animalcules”

14. Early Microscopes • Robert Hooke (1635-1703) • Experimented with microscopes • Observed a network of tiny box-like components in the bark of an oak tree • Described them as “cellulae” meaning “little rooms” in Latin. This is where the term “cell” was derived.

15. Cells in All Living Things • As more scientists observed micro-organisms, they saw cells in every living thing they examined. • Matthais Schleiden and Theodore Schwann came up with this hypothesis: • All organisms are composed of cells. • The cell is the basic unit of human life. • All functions carried out by living things are carried out by their individual cells.

16. Cells in All Living Things • Their ideas formed the basis of cell theory • All living things are composed of one or more cells. • Cells are the basic units of structure and function in all organisms.

17. Microscopes Today • Compound light microscopes • Have two lenses, which can magnify objects 2000X • We use this type of microscope in schools

18. Microscopes Today • Electron Microscopes • Used to see smaller structures inside the cell. • They use beams of electrons instead of light, which bounce off the sample and form an image which is enlarged on a screen. • Today’s electron microscopes can magnify up to 2,000,000X

19. Electron Microscope Images

20. How to Calculate Field of View Medium- Low- Magnification of Low-Power Power= Power XObjective Lens FOV FOV Magnification of Medium- Power Objective Lens

21. Example A low-power objective lens is 4X with a FOV of 4mm. You have a medium-power objective lens of 10X. What is the medium-power FOV? Medium FOV = 4mm X 4 10 = 4mm X 0.4 = 1.6mm

22. Topic 3: The Cell and Its Structures • Multicellular: many-celled organism • Unicellular: single-celled organism • Although these organisms consist of only one cell, they are not simple organisms. • They each have a way of moving, obtaining food, and carrying out functions essential to life.

23. Observing Plant and Animal Cells Inquiry Investigation 2D page 118

24. Cell Parts • Organelles: structures inside the cell • Each organelle has a role to play in the activities necessary for life • Cell Membrane: surrounds and protects the contents of the cell, and helps control the movement of substances in and out of the cell. Cell Membrane

25. Cell Parts • Cytoplasm: jelly-like substance that distributes materials such as oxygen and foods to different parts of the cell • Constantly moves inside the cell • Helps support all other parts inside the cell Cytoplasm

26. Cell Parts • Nucleus: controls the cell’s activities • Contains the chromosomes (genetic material) that directs the cell’s growth and reproduction • Enclosed by a nuclear membrane which controls what enters and leaves the nucleus Nucleus

27. Cell Parts • Vacuoles: balloon-like spaces within the cytoplasm that store food, wastes, and other substances that the cell cannot use right away • A membrane surrounds vacuoles Vacuole

28. Cell Parts • Cell Wall: ONLY occurs in the cells of PLANTS, fungi, and some unicellular organisms • Thicker and more rigid than cell membranes • Made of a tough material called cellulose • Cell walls provide support for the cell Cell Wall

29. Cell Parts • Chloroplasts: structures in which the process of photosynthesis takes place • Photosynthesis uses energy from the Sun to make carbohydrates • Chloroplasts are only found inside cells in green plants and some unicellular organisms. NOT found in animal cells. Chloroplast

30. Cell Size and Function • To carry out their work, cells need a constant supply of materials such as oxygen, water, and food particles, and to get rid of waste • Cells transfer these materials through the cell membrane • Cells need to be small to transfer these materials efficiently

31. Small, Smaller, Smallest • Cells come in a variety of shapes and sizes • To grow larger, organisms add more cells to their bodies rather than growing bigger cells • This occurs when cells divide • Cells are measured in micrometers (μm) • Most cells in plants and animals have a diameter between 10 – 50 μm

32. Topic 4: Fluid Movement in Cells The Cell Membrane • Individual cells carry out the same activities as whole organisms • Your cells eventually make use of the air you breathe and the water you drink • A cell membrane allows materials to enter and leave the cell, and stops other substances

33. Cell Membranes • Selectively permeable: a cell membrane that only allows certain materials to cross it • Permeable: a cell membrane that allows all materials to cross it • Impermeable: a cell membrane that allows nothing to cross it • The STRUCTURE of the cell membrane allows there to be different levels of permeability

34. Diffusion • The structure of the cell membrane controls what can move into or out of the cell. • The Particle Theory helps us to understand how particles can move through a substance • Diffusion: the movement of particles in liquids and gases from an area of higher concentration to an area of lower concentration.

35. Diffusion in Cells • Diffusion also plays a part in moving substances into and out of cells • Example: CO2 particles move across an amoeba’s selectively permeable membrane to maintain CO2 levels in its cytoplasm • Figure 2.13A and 2.13B

36. Osmosis • The most common substance found inside cells is water • Water particles are small and can easily move into and out of cells by diffusion • Osmosis: The diffusion of water through a selectively permeable membrane

37. Osmosis • Water is transported through your cells by osmosis and diffusion to replace lost water in your cells • Water is needed by cells for dissolving many of the substances involved in cell processes • Water moves from a region where it is in high concentration to a region where it is in lower concentration Measuring Osmosis Lab Investigation 2F p. 132

38. Fluid Movement in Plants • Plants need water for photosynthesis • Inside the plant, vascular tissues connect the roots to the leaves • Phloem tissue: transports sugars manufactured in the leaves to the rest of the plant • Xylem tissue: transports water and minerals absorbed by the root cells to every cell in the plant • Xylem tubes look like bundles of hollow vessels (like straws)

39. From Root to Leaf • The root system of plants is covered with fine root hairs • Root hairs: an extension of a single epidermal cell, which protects the outside of the tissue. Water enters a root hair through osmosis when there is more water in the soil than in the root. • From the root hairs, water passes from cell to cell by osmosis until it reaches the xylem tube • As more water enters the xylem tissue, it creates pressure which pushes water up the plant

40. From Root to Leaf • Water is transported by xylem tissue into the stems and leaves • Leaves are the plant’s food producing organs • Most photosynthesis takes place in a layer of the leaf filled with chloroplasts • Why are leaves flat and thin? • There are tiny openings on the underside of leaves called stomata. They allow air to enter the leaf for respiration and photosynthesis.

41. Transpiration • Stomata in the leaf open and close to allow for the exit of water. • Transpiration: the loss of water from a plant through evaporation • This water loss from the leaves needs to be replaced by the roots again when the plant needs water

42. Pulling and Pushing • Fine columns of water connect every cell of a plant, from the leaves to the roots • Individual water particles are held together by attractive forces, which make the plant’s water network behave as a single unit. • Water drawn into the roots by osmosis PUSHES water columns up the plant and water lost from the leaves PULLS water up the xylem tissues from the roots, like a pump.

43. Topic 5: Specialization and Organization • Multi-cellular organisms have different types of cells to perform different functions for life • These cells are specialized: designed for a particular task • For example, our bodies have muscle cells, skin cells, stomach cells, nerve cells, etc.

44. Specialized Cells • Humans have about a hundred different types of cells, each with its own special structure and function • These specialized cells have a structure that fits their function – what they’re used for • Ex. Nerve cells are long, thin cells. They are used for carrying nerve signals from one part of your body to another.

45. The Advantages of Being Multi-cellular • Disadvantages of unicellular organisms: • They have one cell that needs to carry out the function of whole organisms • They cannot grow very large • They have to take in everything they need to live from their cell membranes, so they are usually restricted to aquatic environments

46. Cell Organization • Multi-cellular organisms: • Can live in a wide variety of environments • Can grow very large • Obtain energy from a wide variety of foods • Specialization of cells allows cells to work efficiently • Are very complex, as specialized cells are grouped together

47. Cell Organization • Plants and animals are made of TRILLIONS of cells • Cells with the same structure and function are grouped into tissues • Groups of different tissues form organs • Organs work together in systems • Systems work together to form an organism • The arrangement of cells, tissues, organs, and systems form several levels of organization in living things Cells -> Tissues -> Organs -> Systems -> Organism

48. Tissues • Tissues are groups of similar cells • They are classified according to the functions they perform • Examples: • Muscle tissue: moves parts of the body • Epithelial tissue: (skin) protects the outside of the body and covers some internal structures • Connective tissue: (bone) connects and supports different parts of the body; can be solid or fluid • Nerve tissue: carries signals between brain and parts of the body to co-ordinate activities

49. Tissues Nerve Tissue Epithelial Tissue Muscle Tissue Connective Tissue (Blood) Connective Tissue (Bone)

50. Organs • Organs are distinct structures in the body that perform particular functions • Example: stomach, lungs, heart, kidneys • Each organ is made of several tissues working together • Example: Your stomach is made of four types of tissues (muscle tissues, epithelial tissues, connective tissue, nerve tissue) • Figure 2.24 • Plants have organs too! Roots, stems, leaves, etc.