Study of life

Premedical course - Biology

Biology includes among other

two different approaches

• understanding all via study on the smallest

level of life

Continuity of life is based on genetic information.

Orderliness, structure and functional coupling is encoded in

the DNA molecule

understanding diversity and unity via study

evolutionary processes

Levels of Biological Organization

• Organisms

• Populations

• Communities

• Ecosystems

• The Biosphere

• Molecules

• Organelles

• Cells

• Tissues

• Organs + Organ

Systems

1. Organization

The cell is the basic structural and functional unit of the

organism.

The cell is the lowest level structure, which is able to carry

out all life processes.

Unicellular organism

Single cell –

Bacteria and Protista

- Amoebas

Multicellular organisms

Structure and function are interrelated at all

levels of organisation. Form fits function.

Schizosaccharomyces pombeCaenorhabditis elegansXenopus laevisDrosophila melanogaster

2. Metabolism

Organisms are open systems

- the flow of energy – photosynthesis in producers (plants,

algae (photosynthetic protist), some bacteria) converts solar

energy into energy of chemical bonds for consumers

(animal feeding on plants)

- CELLS manage endless belt of chemical reactions,

chemicals and energy is converted into cellular components

The cell compose, decompose and alter nutritive

substances as aminoacids, lipids, sugars, nucleotides,

proteins and other.

• Catabolic reactions – degradation of nutrients to small

molecules; the cell use some of them as building stones,

useful form of energy is released

• Anabolic reactions use the same energy for

biosynthesis

3. Homeostasis:

regulation of the internal environment

to maintain a constant state

Temperature, water, pH, electrolytes

Regulators try to maintain the parameter at a constant

level over possibly wide ambient environmental variations.

endothermic animals - mammals and birds

Conformers allow the environment to

determine the parameter.

exothermic (both ectotherm and poikilotherm)

– reptiles and some sea animals

Many biological processes are self-regulating, they operate

by a mechanism called feedback, in which an output or

product regulates that process.

Negative feedback – inhibition, level of glucose and insulin

temperature in birds and mammals

Positive feedback - blood precipitation, the function

of blood platelets

Schema to illustrate the positive feedback loop (heavy arrows) whereby activated platelets accelerate thrombin generation, and thrombin in turn increases platelet aggregation.

5. Evolutionary adaptation

Evolution is the fundamental theme of biology.

The ability to change over a period of time in response to the

environment. This ability is fundamental to the process of

evolution .

Ursus arctos horribilis Ursus maritimus

4. Growth and development

Maintenance of a higher rate of anabolism than catabolism.

A growing organism increases in size in all of its parts,

rather than simply accumulating matter.

• Cell growth – proliferation: cell development and division

• Bacterial growth is binary fission, bacterial growth in batch

culture

can be modeled with four different phases

Kingdom Protista Subkingdom Protozoa Phylum Ciliophora Paramecium - binary fission

• Plants Rely on soil primarily for support and water Obtain compounds of nitrogen, phosphorus, and other nutrientsRequire oxygen in the atmosphere and for respiration

• Fungal growthas hyphae on or in solid substrates

• Human, Animal development

The zygote undergoes rapid cell divisions with no

significant growth (a specific process known as

cleavage) and cellular differentiation, leading to

development of an embryo.

6. Response to stimuli

- can take many forms

- the contraction of a unicellular organism to external

chemicals

- complex reactions involving all the senses of multicellular

organisms

- A response is expressed by motion,

for example, the leaves of a plant

turning toward the sun (phototropism)

and by chemotaxis.

7. Reproduction

The ability to produce new individual organisms,

either asexually from a single parent organism,

or sexually from two parent organisms.

Asexual reproduction

is not limited to single-celled organisms.

Most plants have the ability to reproduce asexually.

- binary fission- Bacteria

- budding - yeasts and Hydras

(invertebrates of the order Hydroidea)

budding yeast (arrows)

- conjugation - bacteria may exchange genetic information

Donor’s plasmid (sexual plasmid) F+

passes into acceptor’s cell F-, F-pili

on surface of one bacteria strain – F+,

through conjugative bridge

- parthogenesis, fragmentation and

spore formation that involves only mitosis.

- hermaphroditic species can self-fertilize.

Parthenogenesis

occurs naturally in some species,

including lower plants

(where it is called apomixis),

invertebrates (e.g. water fleas,

some bees and parasitic wasps),

and vertebrates (e.g. some reptiles,

fish, and very rarely, birds and

sharks).

baby hammerhead

Wingless female giving birthAphisAphidGreen-fly)

Sexual reproduction

by combination of genetic material

contributed from two different members

of the species

Each contributes half of the offspring's genetic

makeup by creating haploid gametes.

In anisogamous species, the two sexes are referred to

as male (producing sperm or microspores)

and female (producing ova or megaspores).

Sexually reproducing organisms

have two sets of genes for every trait (called alleles).

Offspring inherit one allele for each trait from each parent,

thereby ensuring that offspring have a combination of the

parents' genes.

AutogamySelf-fertilization (also known as autogamy) occurs in hermaphroditic organisms

Allogamydescribing the fertilization of an ovum from one individual with the spermatozoa of another.

Characteristics of the living systems:

• high organization, orderliness• dynamic system, maintain homeostasis• metabolism - ability of energy consumption and

transformation• grow in terms of kind• ability of development and adaptation

in time – evolutional adaptation• answer to outer stimulus - opened system

exchange of molecules and energy • ability of reproduction, life come from life

Thank you for your attention

Campbell, Neil A., Reece, Jane B., Cain Michael L., Jackson, Robert B., Minorsky, Peter V., Biology, Benjamin-Cummings Publishing Company, 1996 –2010.