For middle graders. (2nd version) Comments and corrections are welcome (English is not my first language). Thank you!

1. Hierarchy in life structures
What are living things made of?
And what do they make, all together?

2. cell

4. The biosphere is
the part of the Earth (crust, atmosphere and water) where life can be found.

5. The biosphere is
the part of the Earth (crust, atmosphere and water) where life can be found.
The biosphere is made of ecosystems.

7. An ecosystem is
a system of living beings living together in a community, all connected to each other and to the non-living parts of their environment (air, water, soil...).
A forest is an example of an ecosystem.

8. Tarkine rainforest, Tasmania

9. More examples of ecosystems…
kelp forest near California
taiga in Russia
savannah in Africa

10. temperate broadleaf forest in Europe
coral reef near eastern Australia
tundra in Siberia

11. cryptoendolyth in Antarctica
desert in Mongolia
hydrothermal vent in the Atlantic Ocean

12. A community is made of
all the living beings (bacteria, fungi, plants, animals...), that live in a given ecosystem.
They are all connected in a network and depending on each other.

14. Ecosystem
Community
Population
Individual

15. Feeding relationships in a salt-marsh community

16. A population is made of
all the living beings of a given species, that live in a given ecosystem.
All the monkeys of the species Macacus rhesus living in some rainforest in Africa are an example of a population.

18. More visualizations of populations…

20. An organism is an individual living being, which is part of a population.

25. A system (or apparatus) is a part of the body of an organism,
performing a specific function.
Examples: cardiovascular system, digestive system, respiratory system, nervous system...

27. More visualizations of (human) body systems…

28. More visualizations of (human) body systems…

29. More visualizations of (human) body systems…

30. More visualizations of (animal) body systems…

31. More visualizations of (animal) body systems…

32. More visualizations of (animal) body systems…

33. More visualizations of (animal) body systems…

34. An organ is a specific part of a system, and it performs a specific function.
It is made of tissues.

35. The stomach is an example of an organ:
it is part of the digestive system,
it is made of epithelial, muscular and connective tissues,
its main function is to start the digestion of proteins found in food.

37. More visualizations of (human) organs…

38. More visualizations of (human) organs…

40. A tissue is a specific arranging of similar cells, specialized to perform a specific function.

41. An example is the muscular tissue, which is specialized in movement.

43. There are 4 main types of animal tissues:
1. epithelial tissue
2. muscle tissue
3. connective tissue
4. nervous tissue

45. Epithelial tissues cover & protect the outer surface of the body/of an organ.
Glands synthesize substances for release into the bloodstream or outside the body. Glands are also made of epithelial tissue.

46. Muscle tissue can contract and relax.
It is made of thin fibers that can shift among each other at the expense of some chemical energy (which comes from food).

48. Muscles, which are attached to the bones or make part of some organs, get shorter upon contraction and longer on relaxation, and so they can move parts of the body.

50. Connective tissues have many different functions:
•they wrap organs and shape them;
•they provide nutrients and oxygen to other tissues;
•they give strenght and resistence to bones and tendons;
•they protect joints from friction;
•they store energy-filled macromolecules… and so on!

51. Nervous tissue carries signals (both electrically and chemically) to/from different parts of the body. Nervous tissue cells are highly specialized: they are called neurons.

52. The central nervous system (brain & spinal cord) is all made of nervous tissue. It collects informations through sensory nerves connected to all the body parts, and in turn it sends out instructions to perform actions (moving an arm, inspiring more deeply, moving one’s eyes…) through other nerves, called motor nerves.

53. Epithelial tissues cover & protect the outer surface of the body/of an organ.
Glands synthesize substances for release into the bloodstream or outside the body. Glands are also made of epithelial tissue.

54. A cell is the smallest part in living matter, it has a special structure and can be specialized for a specific function.

56. Every living being is made of one or more cells!

57. An organelle is a specific part of a cell, where it performs a specific function.

58. A mitochondrion is an example of an organelle: it is the part of the cells which manages energy.

61. Every living being is made of one or more cells!

62. cell
Macromolecules are very big and complex molecules that form the living matter.

63. cell
The most important types of macromolecules are glucids (sugars), lipids (fats), proteins and nucleic acids (DNA and RNA).

64. cell

65. More visualizations of macromolecules

66. More visualizations of macromolecules

67. cell
AA molecule is a stable arranging of atoms joined together. It is the smallest part of any substance which retains the properties of that substance.

68. cell
AA molecule of water, for example, is made of one atom of oxygen and two atoms of hydrogen linked together.

69. cell

70. More visualizations of molecules…

71. cell
AAn atom is the smallest part of an element. Two or more atoms, joined together (belonging to the the same element or to different elements) form the molecules.

72. cell
Every atom is composed of a nucleus, made of protons and neutrons, and surrounded by a cloud of electrons.

73. cell
[ Note that atoms do not look like this, but after all, it is impossible to draw a satisfactory model of an atom! ]

75. The components of a helium atom.
The drawing does not reflect the proportions among the different parts!

76. In proportion, if the atom nucleus is big as an apple, the electrons would move around it in a space about 1 km wide!

77. cell

78. Atoms form molecules
Molecules form macro- molecules
Macro- molecules form organelles
Organelles form cells
Cells form tissues
Tissues form organs
Organs form systems
Systems form organisms
Organisms form populations
Populations form communities
Communities form ecosystems
Ecosystems form the biosphere

79. The biosphere is made of ecosystems
Ecosystems are made of communities
Communities are made of populations
Populatios are made of organisms
Tissues are made of cells
Organs are made of tissues
Systems are made of organs
Organisms are made of systems
Cells are made of organelles
Organelles are made of macro- molecules
Macro- molecules are made of molecules
Molecules are made of atoms