Chapter One/Two Notes:
- Unity and Diversity
- Changes with time
- Structure and Function
Review:
In chapter one, we attempt to observe and define some of the attributes of life. We note that all activities of life arise from living things. Through experimentation and the invention of the microscope, we can now theorize that all living things are composed of cells. Therefore; as basic units in biology we can state that cells are the basic unit of life and that there can be as many as six different activities of life observed by all living things. We also noted that in the subcellular level, cells are composed of molecules and that these molecules help regulate and continue the activities of life. We could say that we have outlined some of the parameters of what links all living things together. Therefor exploring part of one of the big ideas in biology, which is Unity and Diversity. Put simply there are several factors, including cellular and molecular structures and activities, which link all living things based upon cellular and molecular activities.
In this next chapter we are going to explore, the other half of this idea, that idea of diversity.
Developing an idea:
Idea Number One: Activities of Life and Adaptation
From the previous chapter, we noted that one of the activities of life is the ability to adapt.
Adaptations put simply is the ability to respond to changes in or around an organism. These changes allow the organism to improve chances of survival. This ability can be inherited and increase an organisms chance of survival.
Idea Number Two: Levels of organization
| Level of Organization |
Category
|
| Atomic |
There are basic elements found in each living thing,
these include Carbon, Nitrogen, Oxygen, Sulphur |
| Molecular |
Each living thing needs nutrients in the form of
molecules. The nutrients can be classified as:
Fats and lipids-energy and structure
Carbohydrates- primary source of energy
Nucleic Acids- genetic material to regulate cell activities
Protein: structural and regulatory activities
Vitamin and Minerals: help in chemical reactions |
| Cellular |
The cell is the basic unit of life
Cell types can be classified either as:
Prokaryotic: primitive cells, without nucleus and organelles (example: bacteria )
Eukaryotic: more advanced cells, with nucleus and organelles |
| Multicellular |
Cells can combine to form organism which have more than one cell. This increases diversity of cell functions and can lead to organism with specific tissues ( cells all doing the same function) and organs ( group of tissues doing similar functions) |
| Species |
Any organism which look alike and can interbreed with another similar organism, in natural conditions, and produce fertile offspring is said to be a species |
| Population |
a group of organism all of the same species, occupying a given area at the same time |
| Community |
a group of populations |
| Ecosystem |
Several populations interacting with each other plus abiotic factors |
| Biome |
A geographic region based upon a similarity in ecosytems and climate. Example Deserts, Tundra, Boreal forest. |
The next question is:
“ If organism can be so similar, then how do or how did they become so different?” To explain this change we have yet another theory classified under the concept of evolution. Evolution can be thought of as the change of organism over a period of time. This is yet another big idea in biology “ Changes with time”.
Some questions to ponder:
- If organisms change with time, how can that change be shown?
- Is the change shown similarity or diversity?
- Does the change shown directly or indirectly?
- If organism change with time, what is the mechanism that creates that change?
Types of proof in regards to evolution
Like the cell theory, we need proof or evidence to create a theory:
For the theory of evolution we have two types of proof
- Direct Evidence
- fossils offer direct evidence of pathway, or evolutionary history. This pathway can be considered to be a history to show origins of species and how they changed. This history can be used to explain organisms phylogenic or evolutionary history.
- fossils are created due to preserved hard parts of organisms. Fossils can either be original body parts or imprints preserved or “ petrified” with mineral matter.
- fossils can be used to show geological time scales
- fossils can be used to show two types of evolution, called divergent and convergent evolution.
process where original organisms evolve into variety of distinct species. Each new population then becomes a new distinct species. Fossil histories can have gaps and so biologist have to hypothesis as to original species, which lead to a variety of species. Put simply a primitive ancestor has the potential to adapt to a variety of environments through structural changes, behavioral change or changes in reproduction. Divergent evolution often notes changes in structures of fossils to create “ family trees” for organisms.
process of development of similar forms from unrelated species due to adaptation to similar environment. Best example: Marsupials in Australia. Another definition: similar forms in geographically different areas responding to similar environments.
Comparing Divergence to Convergence:
convergent evolution occurs when two dissimilar species change in response to similar environmental conditions and show development of similar characteristics.
Example: Kangaroo and the deer
similarities: in location of eyes, type of teeth, long ears and herd behavior
dissimilarity: marsupial verses placental ancestors
Divergent evolution occurs when members within a singes species change in response to a new and different environmental condition, and each population develops into dissimilar characteristics.
Example: Primate ancestral groups evolving into specific of apes
- Indirect Evidence
Often instead of looking at fossils, biologist can look at current species and use other methods to hypothesis their family background. If we assume that adaptation is an inherited trait, then we can look at patterns of inheritance through embryological , structural, physiological or biochemical evidence.
( remember: How many and what are the types of indirect proof ?)
Each organism starts off as a simple cell. If it divides into a multicellular organism the cells divide and create unique structures. An embryo is the prebirth stage of living organism. Embryology is the study of organisms in their earliest stages of development. In the 1800’s it was noted that several organisms show similarities in their embryonic development. This observation brought forth the statement and a theory of recapitulation:
“ Ontogeny recapitulates Phylogeny”
In simple terms, each organism shows their evolutionary history ( phylogeny) in its own embryonic development ( ontogeny).
- Homologous and Analogous Structures:
Homologous Structures:
Often organisms will have similar structures but these structures serve different functions. This is an example of an indirect proof of divergent evolution. Key thing to remember. Similar structure but different function.
Analogous Structures:
Often organisms will show structures that provide the same function but have differences in structure. Key point, similarity in function but not in structure. This can also be used as indirect proof of divergent evolution.
Vestigial Structures:
Sometimes creatures have structures that serve no apparent function, like hips on snakes or a human appendix. A structure with no apparent function is said to be vestigial.
Physiology:
How organs within an organism work is the study of physiology. For example observing and learning how organisms excrete waste, would be examining a physiological phenomenon. Tissues and chemical reactions within organs can be regulated by specific
